* Make sure all turnbuckles turn freely. Even if they do it's a good idea to apply a little lube in the form of lanocote or tefgel.
* Inspect the bolts at the mast and the tangs (and any other bolt that passes through the exstrusion) and make sure they haven't been overly tightened. This is super-common and really pinches the extrusion. It's also completely unnecessary. Use red loctite, nylon locknuts, spiking the nuts, or best yet - drill and pin with a cotterpin to secure the bolts rather than just tightening the heck out of them
* Inspect the spreader tips for excess corrosion.
* Inspect your roller-furler (if you have one) to make sure everything turns freely and that there are no missing screws, pieces, etc. This includes looking along the length of the foil.
* Make sure there is a toggle on the top end of your forestay. This is very important and frequently done wrong.
*Look for bent or obviously abused clevis pins. This is a strong indicator that things aren't sized appropiately. Don't ever assume that just because it's been one way for a couple of decades and has worked the whole time (or even if it's oem stuff) that it's appropiately sized or set up.
*While you are at the masthead check the sheaves and make sure they turn freely. If you have a halyard restrainer make sure it's located properly and that any moving parts (if it has any) still move.
*Also, if it hasn't been used in years check your running rigging. Do this BEFORE you use a possibly sun-rotted halyard to haul yourself aloft. Tie the ends of the halyard together and reeve them in both directions as far as you can (till the knot hits something) and look at the line carefully. You'll even be able to examine internal halyards this way.
*Also, make sure your winches are in proper working order. This is another to do before putting your life at the mercy of the equipment. As you can imagine, if you are half-way up the mast and the pawls suddenly get stuck in some old grease and the winch can now free-wheel in either direction it may turn into a very bad day. Speaking of which, never trust a snap-shackle to ride up on.