This page began as a usenet article that I posted to rec.food.veg.cooking. Thanks go to Louise Bremner for useful feedback.
There are a few things I've started doing recently that I find really make a difference to a stirfry. The first is that I use a good wok and take care of it properly. I don't scrub it after use, but just wash off any bits that have stuck and are making the surface ragged, then dry and oil the wok. To avoid blackening my teatowels, I do the drying over a low gas flame. The wok being warm also helps to spread the oil over afterwards (you only need a little bit).
This isn't a non-stick wok, by the way, but I find that with this treatment and the cooking technique I describe below, things rarely stick to it in a bad way. When you have used a new wok a few times, it should build up a coating of blackened residue that helps to stop things sticking and contributes to the flavour of things cooked in it. For this reason I've asked my housemates not to cook meat in it.
The second secret of a good stirfry is to cook the food really hot and really fast. I sometimes use long cooking chopsticks, but more often I just use a flat wooden spatula. I don't recommend metal implements. Keep the food moving all the time - your arm should ache when you've finished (unless you do this every day, of course). Don't let it sit in a lump at the bottom of the pan; keep it in contact with the hot sides of the pan (this is why it's made in that shape).
Let it burn slightly (especially onions); it makes it taste nicer. Only add a handful or so of food at a time, so the heat of the pan isn't dissipated trying to heat up lots of room-temperature stuff at once. And I mean it when I say really hot. In fact, the wok should be heated up very well before you even put the oil in to heat. One way to decide how much oil to use is to put a bit too much in to start with, swirl it around to coat the entire inside surface, then pour off any excess. This way, you will only be using the amount of oil that you actually need.
I started using peanut oil in preference to other vegetable oils recently, and it really makes a big difference. It can be heated to higher temperatures without smoking, and it's just a much better lubricant - the first time I tried stirfrying tofu pieces with it I was amazed; they just seemed incapable of sticking to the pan. It is more expensive than other oils (at least here in the UK), but well worth it. I buy it from the Chinese supermarket. It's also known as groundnut oil, and is sold under this name in mainstream supermarkets.
As for how to cut the food (I seem to be doing this backwards), smaller is usually better, as the food cooks faster that way. Long thin strips (julienne) are nice, but you can also do thin round or oval (cut diagonally) slices of things like carrots. Obviously, put in first the veg that will take longer to cook, like carrots and green beans; and the ones that don't need much cooking at the end, like mushrooms and courgettes (although note that you may like your veg cooked to a different softness than me). Don't try to cook too much at once - my wok is average-sized and I wouldn't try and cook a main dish for more than two people in it.
Once the vegetables are stirfried to the consistency that I like, I add other stuff such as tofu, and then a sauce thinned with a bit of water, and then simmer it all together until the flavours have blended and the water has evaporated. The tofu should really be precooked - either prefried (I do this in my nonstick frying pan) or marinated and baked.
I find that it's easier to get up the motivation to do a stirfry if I have the ingredients for a tasty sauce to put with it, such as Quick Peanut Dressing or the black bean sauce recipe below.
Disclaimer: This is not a traditional Chinese recipe; it's just made up. All measurements are approximate, just to give an idea. Do it to taste. I made this one up, but I looked at lots of recipes I found on various websites first. Be aware that the salted black beans are very smelly. Keep the package in something airtight. I get them in a huuuuge packet for about 90p and it lasts for ages.
Serves about 1
Mix it all up well, making sure the beans are mashed in and the salt and sugar are dissolved.