Gold when you are first starting.

When I first started WOW, I thought that 'trade professions' were way cooler than 'Gathering professions', so I took tailoring and enchanting. Cool does not earn the gold. Let me state for the record - in my opinion - Your first toon should take two gathering professions - skinning and your choice of herbalism or mining.
My reasons are:

• Skinning gives you better 'crit chance'. If you plan on taking Leatherworking later, this would be a good choice. Make sure you pick up a skinning knife.
  

• Herbalism gives you self healing. If you plan on taking Alchemy or Inscription later, this would be a good choice.
  

• Mining gives you more health. If you plan on taking Blacksmithing, Engineering, or Jewelcrafting later, this would be a good choice. Make sure you pick up a Mining Pick.
  

• Most players are too lazy to gather their own low level materials, and gold farmers mostly gather the highest level materials (found in northrend). On my realm today - the going price on the auction house for a stack of 20 starting herbs is 88 silver, and takes about 5 minutes to pick.
  
• No one really needs your low level armour or weapons - so trade professions at low levels will loose you money.

The first 'big' town you find at level 5 or so will usually contain trainers. Alternatively 'talk' to a capital city guard and ask for directions to the 'profession trainer' of your choice.

While levelling, you will want to run around with your mini map set to 'find herbs' or 'find minerals'. To do this - click on the small circle that is on the top left portion of your mini map. You will also want to pick up extra bags as you can afford them. Pick herbs and ores, and skin the dead animals - regardless of who killed them.

P.s. I found a good post on this topic - Back to Basics. from Seth at one-copper.com,