Keeping a chart of your temp is definitely the best, and cheapest method. If you are interested in using OPK's: check out the online stores and ebay - you can get about 40 OPK's for around $15: that means you can doo it everyday so you know if you have had a LH surge or not, rather then being unsure because you might have missed testing at the right time. CM can indicate O, however alot of women (myself in included) find their cm changes repeatedly throughout their cycle, particularly if you haven't yet got AF back.