Druid

For the first 10 levels you are stranded with no forms and forced to level as any other caster would, but with improvements going into WotLK you should not have that hard of a time. From level 10 to 20 you get Bear Form that acts as Druids tanking form, building rage from dealing and taking damage and spending it on abilities to deal even more. At level 20 you get your Cat Form that will be your main source of damage for the rest of your leveling journey. Spend Energy to deal damage and build combo points that you can use for powerful finishing moves.

Early game (levels 1-10) you should spam Wrath from range and use your melee swings to finish off your enemies while letting your mana regenerate. Moonfire is generally not worth using unless you are going from one point to the next and have mana to spend, use a combination of melee swings and Moonfire to deal damage while running.

When you get your Bear Form quest done, you can start managing your mana in caster form by using it to heal up, Buff yourself with Nature’s Grasp if you have to fight multiple enemies and cast a single Wrath + Moonfire before swapping to Bear Form and using the rage you build on Maul.

At level 20 you can train your Cat Form and really start making progress. You start using your mana purely for buffing up and healing yourself in between fights. Start off stealthed with Prowl and use Shred from behind your enemy, Rake them for a dot, after that spam Claw to 5 combo points and use them on Ferocious Bite or Rip if the fights drag on enough to get value from full duration.

For your AoE situations where you have to fight multiple mobs, do so in your Bear Form and spam Swipe and Maul.

With levels you will get access to Predatory Strikes and Nurturing Instinct, allowing you to sustain without even leaving Cat Form with instant Regrowths.

At level 40 you get Mangle and you can use that instead of Claw for Cat Form and Maul in Bear Form.

Make use of your free flying at level 60 by visiting your Druid trainer and learning Flight Form.

After getting to Northrend and reaching level 75, train and keep up your Savage Roar buff for a big buff to your damage.

Druids can use any stat to some extent but you should grab as much Agility and Strength for increased damage, Stamina for survivability and rest is optional

Agility > Strength > Stamina > Other

One button travel macro:
#showtooltip
/cast [swimming] !Aquatic Form;[outdoors] !Travel Form; !Cat Form

Rake and Pounce macro:
/cast [nostealth] Rake; [stealth] Pounce

Prowl macro
#showtooltip Prowl
/cast [noform:3] Cat Form
/cast !Prowl

Mangle Macro:
#showtooltip
/cast [nomod,stance:1] Mangle (Bear)
/cast [nomod,stance:3] Mangle (Cat)
/cast [nomod,nostance] Cat Form

Dash macro:
#showtooltip Dash
/cast [noform:3] Cat Form
/cast !Dash

Faerie Fire macro:
#showtooltip
/cast [nomod,stance:1] Faerie Fire (Feral)
/cast [nomod,stance:3] Faerie Fire (Feral)
/cast Faerie Fire

Major Glyphs:

Glyph of Maul
Glyph of Claw
Glyph of Mangle – you should prioritize this glyph after reaching level 50 over one on the other two

Minor Glyphs:

Glyph of Dash – most useful of the three at all stages of leveling
Glyph of Thorns – QoL glyph, so you don’t have to buff every 10 minutes
Glyph of Challenging Roar – Useful for tanking dungeons

Most notable talents to go for are Predatory Strikes and Nurturing Instinct for easy sustain, Mangle for your main ability and Berserk for a big cooldown.
In the restoration tree you get many bonuses for form swapping and a free ability proc along with some nice healing bonuses.