If you have an average cycle, which not many of us seem to, your cycle would be 28 days and you would ovulate (OV) on day 14 (or Cycle day (CD) 14). Your Lutel phase (LP) would be 14 days.
If you have a 26 day cycle and an average LP then you would OV on CD 12. Therefore both the above could be true.
However, if you are not average your cycle could be longer or shorter and your LP could be longer or shorter. For example, my cycle can fluctuate from 26-33 days and my LP is about 10 days. (Your LP length is usually fairly consistent even if your cycle is not)
If you take your temperature every morning, your temperature will drop just after you OV. If you don't want to do this you can make a rough guess and have sex (BD) every day or second day around OV time.
How long is your cycle? I'd count 14 days back from the end of your shortest cycle and start BDing a couple of days before that. Continue every second day until 10 days before the end of your longest cycle and you'll have covered your bases.
So if your last few cycles were 26, 28, 30 and 32 days start on CD 10 and continue till CD 22.
Another way to predict OV is CM . Have a look at the 'how to chart' thread or the Fertility Friend (FF) tutorials for more on this.
You can also buy tests called OPK tests which work a bit like a PG test except they tell you when your about to OV. Again there is useful info on this on FF.
Hope this helps!