Forgot to add, though, that it would be a good idea to get your child accustomed to a sitter if you plan to use one fairly often (even, say, once a month). It would be great to have a "regular" sitter that your child knows and loves. = )
It really depends, if it's someone you know well, then I would say it's fine; like a close friend, or someone from church, etc. But I wouldn't feel comfortable with a teenage sitter yet, not until my baby was a bit older.
I agree with JAXX that's kind of the rule that DH and I have agreed to as well, in terms of babysitters outside of granmas/aunts.
i personally dont leave my kids with babysitters other than grandmas/aunts any sooner than they can talk... i just dont feel comfortable or trusting enough... plus, once they can talk, they can tell me if anything is wrong... just my opinion though... :)
depends entirely on your comfort level. i've babysat newborns before (1 month +) without any problems. also depends on who you get. i've left my girls with a close family friend (adult). don't know if i'd trust a teenaged stranger yet. actually, they start going to an in-home daycare in 2 weeks when she's 4 months.