I made 3 lifestyle changes:
1. Stopped smoking (and haven't started again thankfully!).
2. Took vitamins - Sanatogen Pronatal.
3. Stopped drinking alcohol.
Before ttc both Jack and Ben, I had already been on some sort of health kick anyway, and both times had been going to the gym 3 times a week and had lost weight for about a good year or so anyway. So, each time, I carried on with what I was eating and my exercise regime as I sometimes think that making sudden drastic changes to your diet and exercise throws your body out of sync for a while as it's not what it's used to.
As for the smoking side of it, when I had my first neg cycle, I had a scan done of my follies just before IUI and the doctor said that there was reduced blood flow. I planned to stop smoking in the 2ww, but stupidly didn't during the stims part of the cycle. Anyway, for my second cycle I had stopped from about 4 weeks beforehand - the 2ww which lead to a neg and the 2 weeks leading up to my second IUI. This time I had a scan which showed that the blood flow to my follies had increased 'dramatically' (as the doc put it). I got a positive. Don't know if stopping smoking was the reason, but I'm sure it helped. The scans they were doing were part of a research programme at the time, so don't know what the conclusions were, but it's known that smoking hinders fertility so I think it's a must for anyone ttc, and believe you me, I know how hard it is to stop.
I only ever really drank on a Sat night out before having Jack, never been one for in the house drinking, so that was easy enough to stop.
Jayne x