All you need is a Basal body thermometer, I got mine from ebay for £3 or something, the thing with temping is you have to be consistent i.e taking your temp (under the tongue) every morning at approximately the same time as soon as you wake up before doing anything else.. getting up or moving around too much can affect your temp. I use a free phone app called Fertility Friend which seems to be the most common one to use - you can then input all your AF dates and input your temps each morning and it creates a chart for you or you can download a paper copy and do it yourself.
When you ovulate there will be a dip in temp followed by a sharp or progressive rise in temp confirming you've ovulated. My cycles are quite regular so I also use opks during the week I know i'm going to ovulate to back it up but if you're not sure I imagine it would be annoying doing them all the time!
xx