I hardly drink, so that isn't really an issue for me. I haven't cut back on my caffeine intake either. While I was pregnant, I limited myself to less than 300mg a day. That was what my doctor recommended.
My OB actually said to me as long as I wasn't smoking cigarettes or crack, I should be fine to continue to drink my Starbucks.
Prior to TTC I was a big drinker of alcohol, would usually have 2-4 drinks a week after work. We started TTC in August 2006. I cut down to about one glass of wine a week, worked out all the time, and ate really healthy. After about 18 months of TTC with no luck, we decided to "take a break from TTC". I went on a free for all, drinking all the time, smoking some pot every once in a while, eating bad food, quit working out, etc. After about 4 months of that, I was pregnant.
So, my answer: unless your Dr tells you to cut back on caffeine or alcohol, "drink till the stick is pink". Don't change your life too much while TTC, cause you don't know how long it might take for you to get pregnant.
Oh, and I have always (and still do) drink 1-2 cans of regular Coke per day. My Dr said that 300mg of caffeine is fine while pregnant, and a can of Coke is 34mg. I also have had occasional sips of wine throughout my 2nd and 3rd trimester. My OB says up to 2 glasses of wine a week is fine. Which seems like a LOT to me, I could never drink that much while pregnant.
I tried to cut back on everything while TTC. I'd obviously relax while I was on my period knowing that I was safe but for the most part I was trying to work my way up to being pregnant. Once pregnant I stayed under 300 mg of caffeine though I may have gone over on the rare occasion that I had soda while out to dinner. I stopped drinking entirely while pregnant except for a teeny tiny sip of a friends passion fruit cocktail.
DH just told me no more caffeine at all if/when we get pregnant again because he read a study that showed a thinning of something around the heart (sorry, I was in denial as he was reading it to me) in mice who's mothers had been given minimal amounts of caffeine.