On cooking shows I always see cooks using ordinary pans without non-stick coatings, and nothing ever seems to stick to their pans. But when I try the same recipes at home, my food always sticks.
What can I do to prevent sticking?
It depends some on technique, and some on what you're cooking. And it depends on your definition of "sticking."
Foods that are high in protein (especially those low in fat) are more prone to sticking. So a really lean white fish, which is almost all protein, will want to stick. Likewise, egg whites can stick. To some extent, almost any food that doesn't have a generous amount of easy-rendering fat will want to stick, but higher protein is more sticky.
To counteract this tendency, you need to compensate by putting some kind of fat (usually butter or oil) into the pan in advance of the food. Most people seem to get the best result by preheating the dry pan some, then adding the oil, letting it get up to temperature, then adding the food.
That's the simple summary, but it can get you pretty far.
There's another thing you might run into as well--high-protein items that stick at first will release on their own if you let them cook long enough at reasonably high temperature. So if you throw a steak dry into a hot pan, it's going to stick at first, but as the Malliard reaction occurs (that nice brown crust we love), the steak will actually release from the pan (or mostly release) of its own accord--usually after 3 minutes or so at high heat. The same is true of most meats, but with delicate ones like fish you're probably better off providing more fat/oil than counting on an easy release as the proteins denature.
Finally, what's your definition of "sticking?" If your food literally sticks to the pan, then the technique I gave in paragraph 3 above should help you out. If you are able to move your food around, but find that little bits stick to the pan and turn brown, that's to be expected. That's called "fond" and most people try to retrieve those delicious browned bits by deglazing (putting in a liquid and stirring/scraping as it boils down) and making a pan sauce. And even if you don't want to make a pan sauce, you can clean those stuck brown bits off by putting just a little water in the pan and bringing it to a boil. Scrape the pan with a wooden spatula (or even a regular spatula if you're gentle) while the water's boiling and stuff should come right up.
Depending on the type of pan you're using, you may need to "season" it. If you've got a cast iron pan, even if it came "pre-seasoned", you probably need to improve the seasoning before it works as well as it can.
As discussed in other answers, food sticking isn't all bad. You don't want things to stick and burn, but without any sticking, there's not much browning that happens.
This answer is coming far after the original post but I think I truly have the key to this question. All above answers are correct but missing a key part. First off I work in a high volume restaurant where we pan roast all types of fish and meat in aluminum pans. There really is only one way to be able to cook a half chicken skin side down or a piece of king salmon and have it come off clean without introducing a liquid. The key is to get the pan extremely hot with nothing in it. Once your pan is almost smoking be ready with the oil and your protein. Add enough oil (one with a high smoking point, olive May not be your best choice) to cover the bottom and immediately carefully place your protein into the pan, always dropping it away from you to prevent splatter. Now carefully give the pan a little shake or a swirl and your protein should just glide around the pan. At this point turn your stove down and return to heat. I promise you this will work every time. Essentially what is happening is you are instantly searing and drying the outer edge enough that it won't be able to grab and stick to the pan. Hope this helps someone!
Restoring a non-stick surface to an old frying pan especially one that has lost its' teflon surface is easy. Instead of using steel wool to clean the pan clean it with 1000 grain sand paper. Wet sand the surface until it is shiny. Do this all the time and slowly the surface will become almost smooth as glass. You still need to use a little oil but you will notice the surface becomes highly reflective. We stopped wasting money on teflon buy cheap pans and bought a piece of sand paper instead. If the pan is highly pitted try 320 grain first then 1000.
First, you can use a seasoned cast iron pan. In restaurants, the chefs always -- there are some exceptions -- start with a hot pan with hot oil before they add ingredients because this often prevents sticking.
For a cast or plain steel (not stainless) pans, the surface needs to be conditioned. Only buy pans with a smooth surface regardless of price. Then use metal scourers and spatulas to remove any rough spots. And then regularly heat with oil until it smokes
For proteins, with a conditioned pan, pour in a layer of salt and heat until the salt discolours, discard salt, let cool a bit, roughly wipe out with paper, add a little oil, and cook as normal. This removes any sticky, non-polymerised oils, and stop proteins having something to stick too. With a well seasoned pan properly cleaned this way you will find it better than a coated pan
For carbohydrates, there is not much you can do other than use more oil. Even temperature control, and cooking them as low heat as possible will help