Classic LFG options.
So, as far as I can see there are 5 options for instance group finding in Classic WoW, including 2 addons. You can either group with friends, ask in chat/in person, use the limited in game meeting stones/innkeepers or use an addon.
LFGShout is a simple addon that just posts for you in the chat channels.
ClassicLFG is a more full featured addon that gives you options like spec filters, automatic matchmaking, invite/decline buttons & more.
How do you feel about these & what will you be using?
I'm pretty biased against add-ons. I didn't use them back in the day and when I tried to use them around Cata, many of them were all out of whack and full of errors. I'm just so used to playing straight vanilla.
It can suck to have a group ready for 45 minutes and just needing a single tank to anti-up, but I think it's also a part of the game. It makes you revere tanks and healers a little more and encourages you to roll one yourself to try and fix the wait times.
The one addon I want I don't think exists. I'd love one that allows you to see your hit box and spell ranges as halos on the ground and a red halo around every mobs' threat range, so you can trace around them and avoid them if you wished.