If you play Alliance, you've come to the right place, because in this post I will share a few nice tips for Alliance leveling. Cataclysm will be a bit easier for you if you read this. I hope this helps.
1. In case you don't have too much gold, don't struggle to invest in your Master Riding yet. You will be needing gold to train your skills and some gear, and you don't really need 310% speed, to level up from 80 to 85. If you already have the Artisan Riding skill and 280% flying speed, it should be enough to get you through the Cataclysm zones pretty fast. However, make sure you buy your Flight Master's License. It doesn't cost that much. Being able to fly in Azeroth is important.
2. Make sure your gathering skills are at least level 425 when you pass to Mt. Hyjal or Vashj'ir. To mine Obsidium or to gather Azshara's Veil you will be needing at least 425 in mining or herbalism. Gathering really makes the difference when leveling up. For example, from 80 to 81 you will get about 2200 Exp. from a herb node or a mineral node. Adding that to quests and other Exp. bonuses, over time you will earn a nice amount of Exp. and reach the level cap more quickly.
3. Unlocking the quartermasters of various factions is also an important aspect for Alliance leveling. Cataclysm has brought in quite a few factions and most of them sell helmet enchantments that you will be needing later on. There are guilds or exigent raid leader that won't let you take part to their raids if you don't have your helmet enchantment. So, when you pass through a zone where there's a faction, you should at least unlock the quartermaster there, and obtain at least Friendly standing with that faction, to be able to buy the tabard. The most important factions to unlock while leveling are: Guardians of Hyjal, Earthen Ring, Therazane, Ramkahen and Wildhammer Clan.
4. Especially if you're using an Alliance leveling guide, you shouldn't waste your time with the Crucible of Carnage quest. And this stands pretty much for any elite quest. Unless there's a group ready to go, waiting just for you, that quest is a waste of time. While waiting for people to join for the quest, or trying without healer or DPS and failing, you will be gaining more XP by completing solo quests. You will change the weapon from this quest in one or two days anyway, so why bother?
I'm sure these tips will help you at least a little while leveling in Cataclysm. However, if you want to level up as fast as possible, I can only recommend you to follow an Alliance leveling guide. Following a condensed and optimized quest path, I managed to hit level 85 in less than four days with my last character.