HELP! I'm new. What is the best classes to play in WOTLK?

Hi, im new and havent played wow since i was a kid. I quited after MOP, tried retail, but didnt find it fun at all. So i googled and found this private server. And when i played back in the day, since i was a kid and not english speaker, i had no idea what i where doing. So im asking now if someone experienced players could tell me little about the best classes and WHY they are so good and why i should pick them.

I'm going to start whit making a dps class first, but i will make a healer later if i end up getting adicted to wow again. I dont play tank.

(sry bad english)

I would suggest playing a class that can heal so you can do random dungeon finder and groups faster otherwise you'll have a harder time getting gear. You can run both dps and heal specs meanwhile.

If you want a dps class that could also possibly heal in the future go pala or druid or priest. All 3 have good to decent(shadow priest) dps specs, druid has 2 options even with cat or boomy. If you want to go for a pure dps then hunter could be a good pick, melee dps have a harder life in general since wars/retris/dks are plentifull. Warlock is another good choice for raid utility in demo and you could possibly compete for top dps spots as aff when you are very geared.
Rogues are few, they are fun in pve/pvp, very good dps..but they are melee and thus have a harder time, though 1 rogue/raid should be mandatory for threat management-tricks of the trade-.
In short, if you wanna have dps+ heal dudu, priest, pala
If pure dps don't go retri, war, dk unless you really enjoy it since you'll have lots of competition. Warlock and hunter are pure dps classes which will be required most of the time-warlock being a rare pokemon really-, mage are kind of overpopulated, but then again, it's a big server, if you find a guild you'll have a spot in raids no matter your class/spec.
For a rough estimation from back in the day google wotlk dps rankings, but don't forget the utility you provide to the raid as a non top dps spec(boomy) can often get you more spots than being a mage -who is top dps-.
My 2 cents on the matter :D

i played many classes and in my opinion warrior is by far the best. it's nice to play with war in any spec, all of them are challenging and you don't get bored unlike many other easy classes. it's problem is difficulty in gearing up cause of many melee out there so as first character i suggest you start with one of 4 classes that can be healer too cause all of them are very needed in every raid. shaman and paladin specially

that depends on what you want?
pvp or pve// you want a challenging class or rather an easy one?
i could give u my experience from dk and mage ( with a little bit of rouge and decent info on almost every other class except shaman and priest)
if you'r new, i can tell you to not play a dk, at least not unholy as it is harder to manage your sources comparing to other classes.
i would recommend you give a run to each class for a few lvls before deciding .. paladins may be a good class to pick for both pvp and pve but if u dont like the gameplay, none of that matters,
my first was a mage, it was really hard to manage it( not because it was a mage but because of me :#) but i also think of mage as a good class to introduce u to the game, id say give it a try till 30, which should be easy in a 7x realm, and dont forget to learn teleports in 20. than decide if you want a caster, or a rather physical class..
hf and gl