To carry on from what Bob said.
The choice of tofu is all important, there are so many different kinds and some would be repulsive in a curry, any silken tofu form for instance. Extra-firm is necessary, by all means press out extra water before frying, this is mainly necessary if the tofu you buy comes suspended in water.
Flavoured extra-firm tofu is fine if the flavour will go with the curry sauce. I can obtain a variety called "Tofu Rosso" in the UK, made by Taifun (all their tofu is excellent by the way), which goes very well in curries as it is spiced throughout with paprika and chili, and contains tomatoes and garlic.
Plain tofu will just take up the flavour from the sauce, though if you fry the tofu a lot first then the sauce will not penetrate far. I quite like marinading plain tofu first, unnecessary in the way it is unnecessary to marinade chicken first - but chicken tikka is quite popular, and it works well with tofu.
Do lightly fry the tofu before adding it to the curry, the texture improves for it in my opinion, if you over fry it, it can go hard externally like bacon does.
NB. Are you cooking for a vegan or just curious? If cooking for a lacto-ovo-vegetarian, you can disregard this point, but if a vegan, Korma and Tikka Masala sauces are rarely free from dairy unless they are using solely coconut cream/milk.