Can you give me some good tips how to prepare Fondue without Gruyere/Raclete cheese? What are possible substitutes, and what should I pay attention to when substituting?
It's not a true Fondue but I've done something very similar by taking a white sauce base made with 50 / 50 wine and milk. You then melt in lots and lots of cheese and you get something very nice and similar to a fondue. You can pretty much use any reasonably melting cheese you like although a strong cheddar is very nice. For something really interesting add some Mozzerella and slowly melt it down and you get a wonderful stringy finish.
In New Zealand we made fondue moitié-moitié with mild white Cheddar and Gouda. Very creamy. I think you can make fondue with almost any meltable pure and good cheese, if the original ingredients are unobtainable. More important is the dry wine, a little starch, garlic and pepper. A shot of a good hard liquor also adds flavor. Kirsch (cherry schnapps) is best, but good whisky or cognac also works.
If the wine is not dry enough, give a spoon of lemon juice or even vinegar (!). The acid helps the blending. If the cheese separates, dissolve a tea-spoon starch in the liquor and reheat carefully stirring continuously.
Gouda and Cheddar also work for Raclette.
NB: we are Swiss and not dogmatic at all! :-)
You can also take the standard Swiss fondue recipe moitié-moitié and use all Emmental instead of 1/2 Gruyere and 1/2 Emmental. This came in handy when looking for a way to make fondue for a person who needs to avoid all dairy products from cow and goat milk. In Switzerland, I was lucky enough to find sheep Emmental. I'm not Swiss but I was happy with the result :)