You may choose to write your ad in Word or Notepad on your PC and then copy and paste the ad onto ARFCOM. This way you can take your time writing it and laying it out correctly without having to worry about getting times out or anything.
Pics are always a big help when placing an ad. it shows the seller exactly what they are getting and avoids tons of questions and emails asking for pics.
As far as members who contact you and do not respond after emailing / IM'ing them back, if you have given them sufficient time to respond and they fail to do so, move on to the next person.