I have found that problems with uneven stitches can often be cured by one of three fixes:

1) When my item (or gauge swatch) is smaller or tighter at the bottom than at the top, I know that my foundation chain is too tight. Fixing this is easy, though -- I just make the foundation chain in a hook that is one size larger than the hook I'll be using for the rest of the pattern.

2) I always make sure to pin items together before I sew them (I use safety pins). I pin each end first so I can distribute any unevennness across the seam, and then only after I get it pinned to my satisfaction will I sew it.

3) Uneven stitches sometimes resolve themselves during the washing and blocking process. This is why I always block before assembling, even when I'm using acrylic yarn. I'm fond of wet blocking (which seems to work my uneven stitches out more efficiently than other methods, but YMMV, of course). Wet blocking goes something like this:

First, gently wash your pieces according to the yarn laundering instructions, and gently squeeze the water out (no wringing or twisting, since this will distort the shape of the item).

Second, while the item is still damp, lay it out flat to dry. I pin the corners (using brass pins because they don't rust) and edges out sometimes, depending on if the piece wants to curl or bunch up, and what kind of precision I'm going to need in order to assemble it (I do this especially when dealing with garments).

Then I just let it air-dry. And though they can be useful, you don't need a blocking board -- Heck, I recently blocked a tunic-length women's sweater (worked all in one piece) on a futon mattress, and I have blocked smaller pieces on a towel-covered ironing board.

There are other ways to block, of course. The "pin it out and squirt it with water" method is also easy and quite popular (esp if you have a kid or a sweetie with a squirt gun who wants to feel as though they're helping). Blocking with heat -- well, I've done it (with some fabulous success -- especially on projects made with acrylic yarn), but you need to know what kind of heat your yarn can tolerate so it doesn't melt (acrylic) or start to felt (wool), and you need to have an understanding of what the various types of hot-blocking (using steam, an iron, etc) will do to your fiber or you may get an unpleasant surprise that can't be undone.

There is a fabulous discussion of a type of hot-blocking called "killing" in Couture Crochet Workshop by Lily Chin that features pros, cons, ramifications, how-to, etc., and there are some good blocking tutorials at:

1. http://www.crochetme.com/blog/crochetme/how-to-spray-block-crochet-or-kn...
2. http://www.eunnyjang.com/knit/2006/05/block_me_amadeus_1.html (this one refers specifically to knitting, but the concepts and techniques apply to crochet, as well)
3. http://yarngear.blogspot.com/2005/08/to-block-acrylic-or-not-to-block.ht... (also briefly discusses hot-blocking or "killing" acrylic items)