well, you take your temperature in the morning, at the same time, before getting out of bed (not even to pee, or stand up, or anything) every morning for a few cycles and track it in a chart. you should also make sure you get atleast 3 hours of consecutive sleep (I prefer 5). you can use a special BBT thermometer but I use a digital (its easier) but if its not digital it should be shaken down the night before.
so after tracking your temps over a whole cycle (and later a few cycles) you will (hopefully) recognize a pattern. there should be two phases. at the beginning of your cycle it should be lower (around 97-97.5°F) and then have a spike followed by about 14 days of higher temperatures (about 0.4-0.6 higher than your baseline). your ovulation should be a day before the spike. the second phase is the luteal phase and should be atleast 10 days long.
you also have to keep in mind that many things can mess with your temps. like getting up to many times to pee at night, not sleeping well, not sleeping enough, being sick, wearing different clothing at night, sleeping with or without a blanket, the temperature of the room, drinking alcohol the night before, etc., etc. you can also apparently have a spike and not actually ovulate.
charting your BBT will also only tell you when you ovulated after the fact. the method is used to figure out the average cycle day on which you ovulate. this helps timing 'love-making' (as we call it) ;) and may also indicate a possible problem which you can then talk to your doctor about.
I am also tracking my cervical position, mucus, and opening because it seems to be more reliable and you can track your fertile days as they progress. I posted this question because I use OvuView and it was telling me I should ovulate on the 25th which is what I expected, but then on friday the 25th it suddenly said I ovulated on the 21. this is the problem with BBT. ovulation is detected after it happens. anyways, I also check my cervix and if I were to only consider the related signs of fertility I would assume I ovulated some time the last few days which does not match up with my BBT.
anyways, I hope that helped and if you have more questions feel free to ask :)
hopefully someone out there has some advice for me as well;)
how dose the BBT work i am trying my self but i dont get how that all works can you help me out