Gathering professions (mining, herbalism, skinning) are hands down THE BEST while leveling lower level characters! You can capitalize on people spending A LOT of gold (from your prospective) on the ore/leather/herbs you collect. 10 Gold to a level 10 character for a single stack of 20 copper bars is a big freaking deal at that point, whereas that 10G is total chump change the level 80 guy that is powerleveling his crafting profession. When you finally reach the point where you have all the gold you will ever need, (all that gold you made off of gatherings and the higher quest reward gold you get from high level quests) THEN feel free to drop one or both gathering professions and go from 1 to maximum profession skill in as little as an afternoon in the crafting profession(s) that suit you best.
Keep in mind, you can only track one kind of resource at a time on your minimap. This means that if you choose mining and herbalism, you'll have to choose which shows up on your map and which you have to keep your eyes peeled for on your own.
As for skinning, all you have to look for is the poor baby seal corpse at your very feet! Each skinnable monster you kill or someone else kills virtually equates to more Gold for you without having to go out of your way to collect the goodies from a gathering node.
each gathering profession has its own bonus just for choosing it and becomes active once you reach 75 skill level in it! These abilities also improve for each 75 skill points you earn (at 150,225, 300 etc.)
Herbalism gives you a spell called lifebloom that heals you over time and is on a 3 minute cooldown.
Mining has an ability called toughness that is a passive increase to your stamina.
Skinning's ability is called master of anatomy (or something) and increases your agility or crit chance (can't remember which)
My bottom line suggestion would be to choose Herbalism and Skinning. 1) because I think that lifeblood is the best of the 3 profession bonuses and 2)the "free money" and convienence of skinning.
Especially if you are a Draenei, Lifebloom not only becomes a once in a while life saver, It lets you do rediculous things solo when used in conjunction with the Draenei racial ability gift of the Naaru (another heal over time spell). Example, there is a quest in Lakeshire where you have to kill a level 28 elite orc upstairs in a barracs building who also has a pet bird that deals some serious magic damage. I was able to solo BOTH of them as a level 25 warrior with the extra 700ish hit points i got from the 2 heals. And this was me all green gear! Same character doing the lvl 20 warrior quest in lakeshire where you get drunk and have to go to a cave and back without getting killed. I got jumped by a group of little piggy guys leveled 20-25 while I was still just a scrawny level 20. They run in fear hen they get low on life which naturally leads to more little piggys agroing and attacking me. I made it out alive! In the carnage were the corpses of 7 little piggys! No repair bill, no corpse run, no quest failure....just 7 twinkling bacon sacks waiting to be looted! Soloing group quests and surviving when you are greatly outnumbered not only makes game play much smoother, IT'S FUN AS HELL!