If you can, it's ideal to arrange to do these at a chokepoint in your profession leveling (e.g. when you need Golden Draenite for jewelcrafting, Goldthorn for herbalism, etc.) or as close to max level as possible, since those are usually the points where you'll otherwise spend lots of gold. If you can't do that, though, just make sure to do them.
Some of these quests require you to bring materials with you to the Faire; none of the items are sold on the island, so pick them up before you head out. Here are the professions and the required materials for each, with a slight Alliance bias on locations. In addition to the sources listed, you can get many of the trade supply mats from any Trade Supplies vendor, so check in Mulgore and Goldshire:
- Alchemy: 5x [Moonberry Juice], available from any innkeeper that sells stuff. In SW, the Pig & Whistle in Old Town is good because you can also buy Simple Flour there.
- Archaeology: 15x [Fossil Archaeology Fragments]; you'll need to dig these up from a Fossil digsite.
- Blacksmithing: No mats required; you need an Anvil but can find one on the Island.
- Cooking: 5x [Simple Flour], available from cooking supply vendors. In SW, check the kitchen/back room of the Pig & Whistle.
- Enchanting: No mats are required.
- Engineering: No mats are required.
- First Aid: No mats are required.
- Fishing: No mats are required.
- Herbalism: No mats are required.
- Inscription: 5x [Light Parchment], available from Inscription supply vendors (ask a guard for the trainer location).
- Jewelcrafting: No mats are required.
- Leatherworking: 10x [Shiny Bauble] from a Fishing supply vendor; 5x [Coarse Thread] from a LW or Tailoring supply vendor; 5x [Blue Dye] from a LW or Tailoring supply vendor.
- Mining: No mats are required.
- Skinning: No mats are required.
- Tailoring: 1x [Coarse Thread]; 1x [Blue Dye]; 1x [Red Dye], all available from a Tailoring supply vendor.