Measuring cervical mucous everyday is a good way, it will change from dry to sticky after AF, then creamy and a cloudy colour, then a bit watery, and then gearing up to O it will be like egg whites. It won't confirm you are ovulating but is quite a good way to work out your fertile times.
Start writing down things like you're mood, any cramping or pinching you feel as well. I get really down, tired and moody just before O and then suddenly horny lol!!