1. Its really easy and should be done right from the start of the game. Grab the 2 primary professions, mining and skinning. While you're out leveling yourself you can easily skin the animals. You're bound to eventually enter a mine which will have many minerals. Be sure to mine those ores. You can easily sell off the extra items to merchants or players.
2. Make sure you grab quests every chance you get. You can easily gain additional exp, gold, items and faction while you're leveling. You may even complete some of your quests with out even knowing because they normally require you to kill off mobs or require you to travel/speak to other NPCs. The quests of World of Warcraft are more player friendly than other MMORPGs.
3. Don't spend any money buying World of Warcraft items, equipments and other accessories early in the game. Low level characters from 1-40 are not gear dependent. Along with that fact, you'll get a nice load of items from just completing quests.
4. While you're out leveling, there are certain monsters that has better drops than others. An example would be humanoids. They tend to drop more gold and items than any other creatures in the World of Azeroth.
5. This is the advice I give to friends. When setting up your character, be sure first to read about the characters plus, and minuses; then set up for the strong and weak points. Take in consideration how the character supports himself and how the character can keep going and keep on track to level without losses.
6. Don't spend money on items at the auction during the first 10 levels of your character. Almost everything you will need will drop to you from the quests. Keep your activities balance in the amount time of questing and making products. Then, as you gain money from making and questing you will see your pocket grow.
7. The usual, your character does by the skills he has, whether it is mining, leather, or tailoring. You make and sell your products. This is how you gain, the more you practice your trade, the more gold you have in your pocket, when you sell the items. The higher the level your character is the higher the prices in the prices of your products.
8. Resale, this happened during the holidays. I know of a character that went out and bought snowballs and after collecting many, was selling them at a higher price to others. Later, bragging about the profit. Take advantage of this.
9. Once you level some you can charge others to guide them through lower quests that you can whiz threw. There are many ways to make money, for example you can protect and kill for lower characters.
10. In the group playing, be sure to express your wants and needs, to keep the character going. Drink and food on hand before; so your character can keep going till the quest is completed.