A great article on blocking can be found here. For future reference, www.knitty.com is a GREAT resource for articles on all sorts of things.
Regarding the cast on…you do want your cast on to be as even as possible, but at the same time you don’t want it to be too tight. You can achieve an even cast on by pulling each stitch casted on tightly around the needle, but this will likely end up too tight for the rest of the project. A solution is to cast on very tightly, but use a needle 1 or 2 sizes up from what you’d use for the rest of your project. When you go to begin knitting, use the needle size that you’re meant to and your cast on row will be a) even, and b) not too tight and not too loose.
Hope this helps.