What type of OPK are you using.. How long is your cycle?
BBT you should take at the beginning of each morning around the same time as possible with a basal body thermometer.
You should stay in bed, not get up, or make any big movements, anything that will fluctuate your body temp.
It is best to start at the beginning of your cycle when tracking your BBT.
I recommend joining
www.fertilityfriend.com This is useful site.
You can record all of your temps. and they put them on a chart for you with a base line so it's easier to see your increase.
Also, more info. in depth is on that site, you can watch videos, and they have new lessons everyday that can help you better understand tempting and it's importance of TTC.
Hope this helps, I barely covered the whole topic, but it gives you something to go off of.
Good luck hun.