Rods - need to be checked for worn or damaged rings, spigots for wear, and cork handles may need a light rub down with fine sandpaper.
Reels - should have been cleaned at the end of last season, if not, now's the time to take it apart and clean out dirt/sand and give it a light oiling. And change/renew your leader.
Flies - check your fly boxes for those trusted flies you kept putting back in, to see if any of the hooks are damaged or rusted, even the ones you did'nt use!
Net/s - check that there are no rips/tears in the net itself. If its of the folding type, make sure the net folds smoothly, if not clean or free up where it folds, there's nothing worse than trying to open a net that won't whilst playing a fish.
Finally, how long have you had the nylon/fluorocarbon/copolymer you make your leaders from? 2 or 3 maybe 4 or 5 years? change it! you'll be gutted if the fish of a lifetime gets away because the leader broke.