Do you have the manual? It will help somewhat:
http://www.mossberg.com/manuals/702 715 Rev E.pdf
See pages 14-17.
Basically metal on metal moving parts should get the most attention - those in the trigger housing and bolt. The feed ramp is an area to CLEAN well. Use care cleaning the barrel as you have to do it from the front - inserting the rod at the crown.
There's not much to it really. You have probably discovered that reassembly can be a bit tricky. The manual is some help. Once you've done it a few times it becomes second nature.