If you already have a high level character or a friend willing to give you gold then you can purchase Heirloom items. These items are bound to account and are accessible through the Heirlooms tab using Shift+P. The benefits of these Heirloom items is that they scale with your level keeping your gear up to date without you having to worry about upgrades, and they provide a significant XP bonus.
Also get the Heirloom Mount. Being able to have basic riding speed from the beginning will save you a lot of time if you're starting from level 1. Allied races start at 20, so this is a non-issue for them. It's important to note that Pandaren can not use this mount until they finish their starting zone and pick a faction. Being Horde or Alliance is a requirement of the mount.
If you’re a returning player, consider paying for a month’s worth of playing time—a mere $15—and using the game’s newer Class Trials to see if you still have that spark for higher-level play. While you can also go the “Starter Edition” route for a free, limited romp through Azeroth, you might need a little more than the newbie zones to help you decide whether you want to play through the game’s latest expansion.
Was doing it at 52 on my lightforged paladin and it was easily the slowest zone out of the ones I'd done. Granted, I didn't have War Mode on so I didn't have any PVP talents, but it felt like about 40% of my time was spent waiting around for respawns or wandering around looking for mobs to kill to get a quest item that had like a 5% drop rate. Maybe I just got unlucky but I definitely won't be going to that zone again for future heritage armor runs.
Hillsbrad Foothills is just simply the best place to farm Tin. If you are an alliance player you should still go there, but Northern Stranglethorn is a great alternative. You will see a red zone on the map, that zone is filled with Tin, it's everywhere. When you mined all of it, just go outside of the zone where you can see the little yellowish arrows, mine a few Tin and head back to the red zone because it's most likely that the Tin Veins there are already respawned.
Most classes in World of Warcraft start at first level, but Death Knights and Demon Hunters are exceptions. They start at level 55 and 98, respectively. This alone can shave a huge chunk of time from your leveling experience. Of course, it only works if you want to play a Death Knight or Demon Hunter, but they’re both solid classics that can dish out damage or tank in a group.
I tell you my experience. I'm leveling a priest that it's 60 now and since I have also done some instances (and I have full heirloom set with 20% experience gain bonuses) and been very ahead of the guide, I skipped some zones since they were grey quest for me, well it was a real mess. Missing quests because I didn't to the previous to enable the following. Going in a zone then realizing that I couldn't do that quest because I didn't do the starting quest chain, very unconmfortable. In short what I suggest you it's not to skip areas, or make really sure that you do all the quests required (at least) and check carefully the previous zone you'll going to skip to make sure that you won't have problems with struggling finding where to start the quest chain to sync with the guide section.
No matter your experience level—whether you’re about to experience the thrill of hearing the Stormwind City theme as you walk through its epic gates for the first time, or whether you can spell Ahn’Qiraj off the top of your head—here are some tips and suggestions for making the most of your new life in the World of Warcraft (or your epic, Illidan-like return to Azeroth.)