It has just occurred to me that having read the TTC threads constantly whilst TTC, I haven't been on once since I got my BFP (more than 7 months ago!) to contribute what worked for me in case any other MNers can benefit!
We were one week away from fertility treatment when I got my BFP. We had been trying for ages - OPKs, Zita West's method etc etc.
The thing that worked for us was, without a doubt, the Toni Weshler book - Taking charge of your fertility, and more specifically following her advice about observing your cervical mucous! Its gross - but by god it works. If you aren't observing your CM now, then this is the one thing that you should introduce immediately into your TTC routine. I had a rough idea of what to look for being buying the book so had been keeping an eye out for the few months before, but the month I bought the book I followed her advice to the letter in relation to checking and analysing my CM, and I got pregnant straight away.
I am aware that this sounds like an advert - I promise I don't work for the publisher or anything - just wanted to share the thing that finally got me knocked up!