I put all my receiver packs on the charger and cycle them. I write the date and capacity in fine-line permanent marker right on the pack. That way, I can tell at a glance how old a pack is, and how it's holding up.

I also give all the engines a careful twist of the spinner to feel for any roughness in the bearings. I pressure check my fuel tanks/lines by plugging the carb and muffler lines and blowing into the fill line.

Now is also a good time to check control linkages. It seems I usually find a clevis or two missing its little fuel-line security keeper. Good time for a hinge check, too, especially if you use CA hinges.

It's a lot easier and even fun to fix stuff up now before flying weather gets here and you want to be flying, not fixing!

Good flying,
desmobob