Climb, Charts, Conserve, Communicate, Confess, Comply 
Many areas in Continental U.S. have radar coverage, may need to climb to be in coverage and for better ATC communications. 
If not able to locate self within 15 minutes, get ATC assistance. 
Do not hesitate to use 121.5 and/or declare an emergency before fuel gets low or sun sets 
Make diversion decisions earlier rather than later, however, do not hesitate to divert if needed 
In diversion, get headed towards new destination sooner, rather than have a perfect flight plan to get there first.