Have a look at the Fertility Friend website. there is a program you can use to chart temps and other symptoms and it will predict when ovulation occurs. It gives you a course by e-mail that is good, and explains all the changes that can occur, and what they mean.

I bought a normal digital thermometer from the chemist. Best results are when you can take take you temp at the same time each day, as soon as you wake up, before you move around.