If I want to buy a good multi-purpose chef's knife, which characteristics should I look for?
One of the most important things is a full tang. The tang is an extension of the metal of the blade into the handle. In knives with a full tang it goes all the way through the handle. This improves stability, control, and durability. Cheaper knives with partial tangs will have the handle break off over time.
In a chef's knife you want a blade from 8 to 10 inches long, whichever is more comfortable.
You can also either get a forged or stamped blade. I suggest reading this article on the differences. To summarize, forged blades are softer, easier to sharpen, heavier, and have a bolster. Stamped blades are sharper, harder to sharpen, lighter, and have a welded on bolster if any. With current manufacturing processes forged is not necessarily better than stamped. You should make your own decisions. All crap knives are stamped, but not all stamped knives are crap.
This brings me to one of the most important points: It must feel good in your hand. Don't buy an expensive knife just because it's expensive, or you recognize the name. Go to a store that will let you use the knife, Williams-Sonoma is one that will do this. If you can, bring a carrot in your pocket and actually cut that in the store.
I'll do some research on steel quality and update this later.
I worked in a professional kitchen, so apologies if I go on at some length about knives; when you use them for hours every day, you tend to care deeply about what you're using.
For general use, you want a 7"/17.5cm santoku or 8–10"/20–25cm French-style chef knife. These blade shapes provide the most flexible kitchen use, and these sizes offer a good balance between cutting area and ease of use. Santokus are slightly easier for chopping and vegetables, while chef knives have an advantage for detail work, slicing, and meat. Some people also swear by smaller Japanese or Chinese cleavers, which take a little more practice to use, but fill the same role.
Care and Sharpening
People reviewing knives never mention the most important part of buying a knife: caring for it! After 6 months, how you maintain and use your knife matters more than which one you purchased. Proper care, honing, and sharpening are the difference between effortlessly cutting slices so thin you can see through them, and mashing tomatoes rather than slicing them. Let me give you a couple extreme examples from personal experience:
If you're buying a quality knife, then you ought to be buying quality tools to maintain it. A smooth steel or ceramic sharpening/honing rod is absolutely critical, and costs under $30. The knife should be honed regularly at an angle slightly steeper than the primary bevel. generally daily or before a major task. Regular honing prevents the edge from coming out of alignment and folding over, and a ceramic rod will slightly sharpen it. Cheap and grooved butcher's steels can rapidly worsen a knife, by chipping it away with their coarse surface. This is especially a problem with harder Japanese steels.
When the knife becomes dull enough that honing won't restore it, after a year or two, get the knife sharpened by a professional, or invest in a professional-grade sharpening system. Putting a more acute angle on the knife (15 degrees per side instead of 20-23) will produce an even sharper result than normal; in many cases this will produce slicing power superior to the original factory edge.
The primary quality here is hardness, as measured with the Rockwell C hardness test, abbreviated HRC. Hardness determines how acute an angle you can sharpen the knife to, which in turn determines how sharp it will be. Superhard steels can go as low as 8 degrees per side, while softer steels may be better served by a comparatively dull 20 degrees per side. Harder steel also will retain an edge against wear for longer.
Japanese steels are known for being harder but more brittle than German steels. This trade-off means they require special care to use and sharpen; I've heard of a tortilla chip taking a chunk out of a particularly thin and hard knife. Japanese knives should NEVER be used to cut hard materials, particularly bone, or to pry at things. They can even shatter when dropped. In contrast, softer German steels are easier to sharpen, and more forgiving. They tend to bend rather than breaking, and can be restored more easily with honing. As I said before, edge maintenance matters more than steel. In the hands of a gifted sharpener, low-grade stainless steel can become quite sharp; however, a better steel will allow them to refine the edge to an unbelievable result.
Construction: Forged vs. Stamped Knives
Blades may either be forged or stamped. In the past, stamped knives were generally of inferior quality, but improvements in manufacturing mean that extremely high quality stamped knives are now available. Stamped blades are generally lighter and thinner; due to their thinness they may cut more easily than thicker forged blades. Common manufacturers of stamped blades include Global, Victorinox, and Shun. If you want a knife that is easy to maneuver, precise, and not tiring to use, a stamped blade is for you.
Forged blades are generally heavier and more durable, and some people find the edge is easier to sharpen. The thicker blades survive wear and sharpening longer than thinner stamped blades. Wusthof and Henckels are traditionally known for their forged knives. Forged knives often feature a bolster, a raised ridge between the blade and the handle. A bolster makes the knife considerably stronger, but also more difficult to sharpen, and it reduces the usable knife area slightly. If you want a knife that is heavier, with some momentum to help your cutting, and durable against punishment, a forged knife is for you.
It is a personal choice whether to use a stamped or forged knife. With proper care, both types will stay sharp and last a lifetime. There is also some crossover; stamped knives may also have a bolster welded on to them, and some manufacturers will produce both stamped and forged knives. The forged version is generally more expensive, due to higher manufacturing costs.
Personal bias: I prefer the sharpness and lightness of stamped knives. They let me do 15 or 20 pounds of julienne onions without fatigue.
Construction: Handles and Balance
A knife should be evenly balanced when you wrap your fingers around the handle and pinch the blade with thumb and forefingers. If the knife tips toward the handle or the blade, it is off-balance and will be less comfortable to use. As far as construction, "full-tang" knives are preferred; these have blades extending fully into the handle. This makes the knife slightly heavier, but provides a stiffer, more durable construction, and makes it much harder for the handle to break off the blade.
Handles come in a variety of materials, including plastic, wood, steel, bamboo, and bone. There is often some texturing to help grip a handle; this can literally be a life-safer (or at least finger-saver) if you work with greasy, slippery sides of bacon, meat, or fish. In my experience, the Victorinox Fibrox handles have fantastic grip even when oily, and absorb impacts. In contrast, the dimpled steel handles of the Global knives are worthless and should carry a "slippery when wet" warning. The most common wood or synthetic handles fall in between, with Wusthof's Classic line being more or less the standard.
Wood and bamboo handles deserve special mention: although these are beautiful, they also require special care to avoid wearing out or splintering. They should not be washed in a dishwasher or allowed to sit in water; although this is true for any quality knife, it goes doubly for these materials.
Specific Knives and Reviews
Cooking for Engineers and Cook's Illustrated both did excellent knife reviews. My main knives are a 8" Victorinox Fibrox and a MAC MTH-80 granton-edge. Both definitely deserve their strong reviews; the Victorinox is a phenomenal value, and the MAC takes an absolutely unbelievably edge. I've met duller razor blades.
Consider stainless vs. high carbon steel
Stainless knives are nice because the edges might be more stable because they won't rust and tarnish. They can be dishwasher safe (as long as some care is taken so they don't bang into other things), and are a bit more durable.
High-carbon steel is better at keeping an edge because the steel is harder. The edge will remain sharp for more cuts than the stainless. The downside is that the steel can corrode if lots of acidic things are cut, or the knife is not cleaned after use. Stainless is considered more difficult to sharpen properly than steel, but you probably shouldn't sharpen your own knife anyhow (honing, on the other hand, you can and should do).
Some manufacturers make a laminated blade, in an attempt to balance the benefits of both. I've only seen this in Japanese knives that are fairly expensive, but it seems a good idea: a thin sheet of very hard steel is sandwiched between a pair of soft stainless pieces. The hard steel is too brittle to make a blade from, but keeps an edge very well. The stainless adds strength to the knife, and keeps everything shiny.
Knives come in a wide range of shapes, from a blade that barely extends down from the handle to the large rounded (Japanese-inspired) shapes with a flat blade. This is a matter of personal preference. I do a lot of chopping, so I prefer a flatter, wider blade that gives my knuckles some clearance over the board while chopping.
I find the scalloping along the blade, which is fashionable these days, to be unnecessary, but others seem to disagree on this. I don't slice enough delicate things to notice any effects.
Knives come in hundreds of shapes and sizes. For a chef's knife, you probably want a 8-10" blade, no serration (that is important), and it must be comfortable in your hand. I have known people who do most of their cutting with a large Chinese-style vegetable cleaver, and they are perfectly able to do anything I could do with an agile 8" chefs knife.
For a good quality knife, you want to avoid stamped blades. Stamped blades are usually thinner, made of cheaper steel, and are more flexible. Forged blades are heavier, more durable, and easier to sharpen. The knife sets sold for $10 at Walmart are stamped and suck. Avoid them. A forged blade will be thick on the dull edge, and will taper more or less uniformly to the bevel of the cutting edge.
If you plan to put the knife in a dishwasher (not recommended--they get banged into other things in the dishwasher, dishwasher detergents damage non-stainless steel), get one with a plastic handle. Wood doesn't like dishwashers.
You will want a honing steel. This is used to correct the edge (it bends a bit during use, the steel straightens it out). They are usually rods of hard steel with a handle.
Here is my favorite cheap knife. Only $30 and it is awesome.
This is the best info I could find.
Also look at Kitchen-Confidential-Adventures-Culinary-Underbelly from Anthony Bourdain:
Also look at this online resource for knife choices.
Most important thing is comfort of the grip. If it's not comfortable, you will not want to use it. If you don't want to use it, you have wasted your money. A "fancy" knife that doesn't get used is a paperweight.
Besides a good sharp blade and a solid comfortable grip, your preference for heavier vs. lighter blades will determine your choice. That said, over the years CooksIllustrated / America's Test Kitchen has reviewed knives and consistently recommended the inexpensive Victorinox (Victorinox Forschner) Fibrox 8-Inch Chef's Knife, particularly if the question is "what one knife should i buy?" Top-quality at a bargain price.
Even when reviewing more expensive "innovative" chef's knives, they still found little to justify the additional cost. Reviews of hybrid chef's knives produced some standouts, for a cost. The final results are on the pay side of their site, but you can get the jist of it from the free articles.
What to look for? From the reviews: