Hmmmm shells LOL
I remember the first day i had a shell up i was like wtf but if u notice most ppl still dont know how to do it
Here is a key thing check the server php.ini files to see what is all disabled
Check the Servers version and do a quick scan for a exploit try to backdoor the connection most shells backdoor script will never work try to gain a perl backdoor connection. After that if succesful you will be group APACHE or whatever it is
after that your fun begins