Someone responded to your ad, now what?
First read the response carefully. There's probably more to the person than they were able to convey in one response. Also keep in mind that some people are better at describing themselves than others are.
After reading through the response a couple of times, you will have formed one of three opinions.
1.You aren't interested
2.You might be interested, but would like more information.
3.You are interested, and want to get to know the person better.
If you aren't interested, the easiest way out is to just not reply. If you are like I am, and feel that you should at least reply, then please be considerate. It may have taken a lot of courage for the person to write to you. Take it as a compliment, and try to leave the person feeling good about him/herself. That applies to someone that might approach you personally as well, as long as they approach you politely.
If you might be interested, decide what else you want to know, and start asking questions. Be prepared to answer some as well. Ifyou decide after a few exchanges that you don't want to continue, again try to be polite. At least with e-mail it is possible to just not write anymore without being overly rude.
If you definitely are interested, try to keep the conversation going. Be open, honest, and give the person a chance to get to know you.