Cautious v. Over-the-top

There's certainly no shortage of warnings during pregnancy.
Don't eat lunch meat or too much fish. Don't take pain relievers, except the occasional Tylenol. Don't sleep on your back (past a certain point in the pregnancy). Don't do abdominal exercises... darn.
I consider myself a fairly well-informed person. Or maybe I should rephrase. I considered myself a fairly well-informed person before I started reading about what was happening inside my body and what I need to watch out for.
I definitely did not know lunch meat can carry listeria, or that it's a major risk for pregnant women. But I haven't visited Jimmy Johns or Subway since I found out. (Though I expect Brian to deliver a Beach Club to me the day after the baby is born!)
I'm trying to listen to the advice as I learn it. Obviously I want to have a healthy baby and for it to have all the advantages in the world. But I'm wondering how far I should go in being cautious during pregnancy?
Do I avoid standing near microwaves, as one source suggested? Not that I'm spending a lot of time hanging around microwaves. But can I stand by the one at work during the two minutes my lunch is heating up?
Do I avoid artificial sweeteners and diet pop? What about the small amounts of caffeine I'm having (not even every day!)... Is that something I'll regret down the road?
Honestly I try not to stress about this stuff too much. But I can't help wondering if I'm doing the right things and avoiding enough of the wrong ones.