Whether your starting your first character or starting an alt it is important to choose the right professions to help you. Most gold makers agree that the best choice is to choose a gathering profession while leveling. This allows you to make gold while leveling as opposed to spending gold to level a crafting profession. It is much easier to power level your crafting profession once you hit max level. There are three gathering professions you can choose.
Mining is probably the best profession to choose while leveling. There are multiple crafting professions that depend on mining to create their crafted items. These include Blacksmithing, Jewelcrafting, and Engineering. Each node of minerals that you mine grant additional experience for leveling. Stacks of ore sell pretty well on most servers.
Herbalism is the second best profession to choose while leveling. There are two professions that depend on this. Alchemy and Inscription depend heavily on herbalism. Herbs sell very well once past the starting areas. Each herb grants additional experience for leveling your character.
Skinning is the third gathering profession choice. Skinning is not an ideal choice for leveling your character. Skinning does not grant additional experience for each leather skinned. Skinning and leathers do not tend to sell well until the very high levels.
I would recommend that you learn mining and herbalism as your professions while leveling your character. The experience gained from these will help to level your toon much faster. I would only recommend skinning if you plan on picking up leatherworking at a later time.
If you don’t believe that this experience gained would level your character faster, you could not be more wrong. When Cataclysm launched I leveled my miner from level 80 to level 85 in three days doing nothing but mining. That was faster leveling than I was able to make on my main simply by questing. While prices vary by server you will be amazed by the gold to be made by selling your ores and herbs on the auction house.