There are professions you can train in to make money in the game. You can be an herbalist to pick useful plants; an alchemist to make potions; a miner to mine ore; a blacksmith to craft armor; a jewelcrafter, who can cut gems that can be socketed into certain items to augment them; or an enchanter, who can enchant items to have bonus stats or effects.
Some people have made arguments that quest blues can sometimes be more powerful than heirlooms, especially with sockets. I'm not convinced. The simple fact that you never have to even look at quest rewards will save a non-insignificant amount of time over the course of leveling. Also of consideration is the value of enchanted gear never having to be re-enchanted.
You may be starting out ...or this may be your next alt to walk along the world of Azeroth. But while some players of "World of Warcraft" may wish to enjoy the ride and level at their pace, many others want to get to level cap as soon as possible. Many questing guides exist for this reason. Many guides show exact routes and quest information to hit each area as quickly and efficiently as possible.
Fishing requires much time and does not yield much profit until its later levels. Unless you enjoy it for its own sake, avoid seriously delving into fishing until your level limit. It is not a bad idea to do a little when starting out a new character on a new server, though - the gray items you fish up sell for good money to a starter, which can help you out with your other tradeskills.
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