AD, my sister in law found
Taking Charge of Your Fertility helpful in conceiving, and she recommends their chapter on gender selection (although I'm not sure if they actually tried it). You might also check out
How to Choose the Sex of your Baby. It's the "classic" in gender selection that everybody recommends.
That said, you can probably find all the information you need on the web. Personally, I used the tips found on
BabyHopes.com (culled from the above-referenced book, as far as I can tell). They also sell the cheapest ovulation predictor and home pregnancy tests I could find on the web, and they're extremely good tests. (Up to twice as sensitive as the drugstore variety.) Ovulation prediction is the single most important factor in gender determination, so in order to pinpoint the exact day you'll need dozens of the little pee-strips, take my word.
Not to sound like some sort of infomercial, but we followed the advice on the BabyHopes website (linked above) and were -- obviously -- rewarded with the son we dreamed of. Granted, we had a (roughly) 50/50 chance, but I like to think that we helped things along at least a little.
IMHO, trying for a boy is much more fun for the lady than trying for a girl.

Good luck!
Edit: For the more clinically-minded, here's one last link:
http://www.childbirth.org/articles/sex.html#sum