Hi, I'm not an expert on this as I'm only just about to start temping but I've read up on it a lot. You need a thermometer that measures your basal body temperature (you can get these off Ebay). You need to take yr temp first thing in the morning before you do ANYTHING (so basically as soon as you wake up, don't get up to go the loo, sit up or anything). Try to take yr temp at more or less the same time every day as the longer you stay in bed effects yr temp. You preferably need to have had at least 3hrs of solid sleep before you take yr temp.
A good site to record yr temps is fertilityfriend.com - you can sign up for free. This will tell you when you ovulated based on yr temps.