Are you including enough SASE postage with your QSL??

http://www.k4hb.com/postage.html
A great resource to see if you’re sending enough Green Stamps or IRCs to a particular DXCC entity in order to ensure that they’ll send you a QSL Card in return.

Do you even know if the other ham is going to reply to your QSL??

http://adok.dyndns.org
Check this page to see if the station you are QSLing is known for replying. While you’re there, upload your log file!