Max over many
Some folks plod along, raising many toons and professions little by little, but this is not an optimal way of driving your gold earning power. Better to level a toon to max, along with its professions (preferably productive ones), than to inch along a lot of toons and professions at the same time. There are big advantages to being among the first to hit a crafting milestone or luck out with a rare recipe early. The quicker you reach the cutting edge or limit of a profession, the better. There is more value in end-game items.
Early bird gets the worm
This is the extreme version of “max over many.” In some cases, players that are first or among the first to get an item – or a recipe – can make boatloads of money before more of the item becomes available, or more crafters get the pattern. The same holds true if mats are hard to get – limited supply will help drive the price of the items that require those mats.