1.)Fishing license: Seriously, sometimes it's overlooked or forgotten about all together. You want to make sure you're legal to fish where you're going.
2.)Fly Rod: Clean it up, make sure you don't have any loose guides, etc.
3.)Fly reel: Dig it out & take a look to make sure it's still clean & working good. Now is the time to find a problem with it - not along the stream. If you haven't greased or oiled it all winter, do that now.
4.)Waders: The water's very cold this time of year. Make sure you don't have any leaks & fix any that you find. You won't last long in the cold water with a wet leg & foot.
5.)Fly line: Make sure it's clean & ready to go. If it's old, stiff, & cracking then go get a new one before you head out to the water.
6.)General Tackle: Go through your fly boxes & make sure you have everything. All those flies you tied this winter - don't leave them at home because you forgot to put them in your boxes. Make sure you've got enough leaders & restocked your supply from last year. Split-shot, too. This is the last time to go through your vest or bag to make sure you have what you'll need.
Sometimes we get so busy that we forget to look at the obvious things before we run out the door on our first fishing trip of the year. That can lead to major disappointment. So take the time to go over your equipment before hand & you'll be glad you did. Good luck on the stream & save some fish for me!!