You really can’t level that well as Prot until you get into your mid 30s. That’s when you get into AOE Tank/Grinding – which is a very efficient way to fight multiple mobs. (Remember Questing is still faster than grinding, But many quests require you to kill X mobs or collect Y drops… Doing it in 2 – 3 pulls of 5 mobs each is very helpful.)
Others will disagree, but here’s my opinion. Go Ret for 1 – 70. I leveled as Prot and it WAS a bit slower than Ret. Plus you CAN tank as ret until you get into Outlands. (Plus nearly every party you enter before Northrend will likely have at least 1 OP member.)
Ret does great damage, can tank Vanilla wow Easily, can tank TBC if you have a good group, and is just a great way to move through content.
Spec for +STR, +STA, and +Crit. (I don’t think you can find much +hit stuff early in the game.) Try to stick with plate, but if a piece of mail or leather REALLY boosts your stats, slap it on. You are a DPS – you shouldn’t be getting hit much anyway.
If you choose to AOE tank – Google it and follow the instructions. Start small – AOE grind 2 guys, then 3, then 4… Your limit should be where you can end a fight with >50% health and mana. Anything below that is getting risky and MAY cause excessive downtime through eating/Drinking.