Melody - There are a couple of threads with info. This is the info thread, and This is the gender swaying buddies thread.

I also used a copy of How to Choose The Sex of Your Baby, by Dr Shettles which explained the best ways to use OPK's to pinpoint when O happens. To pinpoint accurately you need to be charting your BBT as well. Then when you notice a pattern you can take a month off every now and then.