As for pre-conception vitamins, its REALLY important to get your folic acid for three months PRIOR to conception - helps your eggs be nice and healthy for when you conceive. Most all multivitamins have the 400 of folic acid necessary. DH's sister has severe mental and physical retardation as a result of a neural tube defect, which was most likely caused by insufficient folic acid in his mom's diet, so though I stink about taking vitamins regularly, I am rabid about the folic acid. Also, folic acid is really the only supplement you HAVE to take during the first trimester, so if the other vitamins are making you sick to your stomach (usually because of the iron) you can just take the folic acid for the first trimester. My mom's OB friends did this when they were pregnant...
For those TTC and already have a kid - how do you feel about having another? I am excited, yet I wonder if I could possibly love another LO as much as my daughter, and worry about balancing time between the two. DD should be close to going to pre-school part time, so at least she will have that big-girl thing to be doing.
I was nervous about having another baby when I was pg with #2. I felt like I wouldn't be able to devote myself to dd1 in the way that I had before. I felt that she would resent her baby sister. It really wasn't bad, though! dd1 transitioned fantastically and now, at ages 2 and 4, they are BEST friends. I'm more nervous about #3, when the kids outnumber the adults you're in trouble! haha.