Well, my experience with tofu is the opposite ... it's never all that fresh in the packages from the grocery store, and it sours pretty quickly. Personally I wouldn't eat it if it's past the expiration date, or even if it's inside the expiration date but the water is yellow and bubbly or sour. Silken tofu in the shelf-stable packaging probably keeps a long time, though.

It depends on what you want to do with it. If I want a squash or carrot bisque with tofu, I just break up the cake into chunks after the vegetables are tender, throw it in and blend the whole thing with a stick blender (don't forget to pull out the bay leaves or bouquet garni before blending - btdt and it wasn't pretty ). For burgers, I drain it, then squeeze out as much water as I can by hand, then just crumble it and mix it with the other ingredients. Pretty much the same thing for quiche. For sauces or dressings, you'd want to blend it smooth first and then mix in your other ingredients and warm it.

Don't go overboard with soy though. It can aggravate PMS and other estrogen-dominance issues. Some is good IMO, but there's such a thing as too much.