Proper woks can be hard to find. They shouldn't have a flat bottom but a curved one. (Otherwise it's just a frying pan, or a saucepan, with a posh name). That's to ensure really good heat distribution, which is also enhanced by using a heavy wok made of either iron or steel of a substantial thickness. Non-stick woks rarely meet these requirements. Look for a heavy wok, with a curved base, made from either iron or steel. Then 'season' it, to make it non-stick:
http://www.bbc.co.uk/dna/h2g2/A791282
Chris