First off, as others have said, its SO fast already atm, there barely is any need to go really serious about try and max things beyond the basic.

The basics :

- Send 4 big bags to your newly created alt, you will need the bagspace later and its nice to not have to constantly destroy items because your bags are full.
- Sort out inventory during travel time, so once you are at your destination all you have to do is let your addon sell all the grey items and the bag you filled with crap you dont want anymore.
- upgrade your riding skill whenever you can, you will be surprised to know that about half the time you play while leveling is traveling, less time spend on this means less time spend in leveling, same goes with the item that increases mount speed !
- play with heirlooms. They dont give a bonus xp anymore, but they will scale with your level and provide other nice bonusses, makes sorting the bags mentioned earlier so much easier since the items will always be worse than your heirloom or their bonusses.
- Enchant / gem your heirlooms if you want to use them on more than one character. Chances are you have quite a stash laying around and some enchants arent expensive at all.

Now that you have created a character and mailed all this crap above to the char, you start.
from level 1-30 its pretty darn slow for todays gaming standards due to no flying.
For this reason I would suggest to either go to silverspine which apparently is great or pick an expension of these four you like most : Wod - MoP - Legion or BFA
At level 20 go to your stormwind/orgrimmar , learn riding AND turn on warmode for that extra 10% XP

By all means to do the WOD intro which - with the 16th anniversery buff - is about 6 levels and you are still free to go wherever you want after.
I created a char to do some of the missing zones for my loremaster achievement. As others have said , you will do 10+ levels per zone so you really wont be doing many of them this way.