Welcome Code - I think the main objective with playing Classic is to choose your own adventure. Take your time, play what you enjoy and focus on being polite and you will go a long way in Classic. If I was to offer advice on leveling for your first character, Hunter is fantastic. Druid (leveling as feral) is also efficient, versatile and fun. Spend time PvPing, exploring, doing 5 man dungeons and try to get into a friendly 'leveling' guild.

I am excited for you to experience it for the first time, I am sure you will find your place in the world!

what are some rookie mistakes I could avoid, how do I get around without being lost

Make mistakes! Get lost!
Honestly, it really is all part of the fun and whilst sometimes it will be frustrating, you'll have so much more fun in the end if you have those experiences. You will feel yourself getting better at the game which is an extremely rewarding feeling!

Hi Code,

I think with Classic getting lost is half the fun!

That being said, there are some pretty useful guides on BC that you should probably check out:

The only thing I would suggest is that you take a good amount of time to consider what class you want to play, it's a long road to level 60 and you don't want any regrets!

This is an excellent point, you'll probably want to avoid rolling a char, realizing you don't like the class, then re-rolling. It's essentially a massive time sink and will make sure you fall behind the curve if you plan to play on release.

what are some rookie mistakes I could avoid, how do I get around without being lost

Make mistakes! Get lost!
Honestly, it really is all part of the fun and whilst sometimes it will be frustrating, you'll have so much more fun in the end if you have those experiences. You will feel yourself getting better at the game which is an extremely rewarding feeling!

I developed a poor BFA mentality over time. I guess I just got to lay back and enjoy. It's been a long time since I have in a MMORPG.

Besides what everyone has said above.

I would add, which you may have experienced a little in wrath, is everything is dangerous!
You are not this immortal being like in Legion (Last time I played), where you can walk into a zone and gather 20 mobs and kill them all even when wearing greens and under leveled (exaggerating to a point but close to the truth).

In classic/vanilla and TBC and even a bit in WOTLK you could only pull one and maybe two mobs at a time while questing or farming at your level.
Even pulling two you will need to control the other one or it will be a race to see who kills who. Depending on classes some things are easier than others. Yes frost mages could aoe farm well with all the talents to slow mobs and shatter but one wrong move or if a mob or two resist, your toast. Grouping up and socializing was a big thing back then while questing and especially doing group quests because back then group quests meant group quests.

The only real mistake you can make is picking a class that doesnt suit you. Not because you wont have fun with that class, but because you will have fun with it. So you dont even realize what youre missing out on if you picked a class that actually fits you.

Don't be afraid to let dungeon groups know if it's your first time or if you're just not familiar with the instance. Most of the time someone will explain fights to you before hand, and that's preferable over wiping while you quietly figure it out.