I have learned all these from an experienced and talented master hand. First off, before you try this method, download the addon called Gathere. It will make a spot on the map for you of your mined veins. Once a vein is mined it will spawn at a later time. Gatherer is important for what I call, Path Mining
    Path Mining- In order to be efficient and fast at leveling mining, you must use gatherer to collect all mined veins in the area you are at. Once you have combed at least half the zone of its metals, select a starting point on your map where there is a good amount of ore. Then, try and hit all of the other veins in a circle pattern so you will end up where you started. If you have a big enough path, enough time will go by for the original ore sources to sprout again, thus allowing you to hit the path again. Paths are always in a circular pattern or at least a shape of some sort (rectangle, triangle, whatever)
    Also note that rare minerals like Silver, wow Gold and True-silver spawn where their perspective ores spawn. Each time a node spawns, it has a chance to be it is rare mineral.
    As for Copper, there are three places you should care much about. The first one Durotar, right outside Orgrimmar, there are tons of copper veins everywhere. Also, the hills outside of Silvermoon and along the scar, which have Copper veins in plenty. However it is not near as much as the mountains surrounding Orgrimmar.
    As for Tin (Silver), just remember the followings. In STV, there is a little to be found around north it. In Ghostlands, you must search along the scar going back and forth. My recommendation lies in Thousand Needles, there are Tons of Copper, tin and Iron veins here. Just let gatherer do its job and make a set path. Make sure to check any spot including the edges, with rocks or mountains protruding. Just look at your map.
    As far as Iron (Gold) is concerned, we should pour our attention at Badlands and Thousand Needles, since at STV, you can find nothing. At lower levels, you should stick to Thousand Needles if you have found a path with iron in it. When at Badlands, around the middle and not along the edges, you should try to hit all of the large mountains in the middle areas of the map.
    As for Mithril (True-silver), the first place is Badlands. Here you are supposed to make a complete circle on the edges of the map where the mountains surrounding Badlands are. There is so much Ore, and True-silver spawns a lot here. This is a path that will take a while to complete, and all of the ore will be back by the time you come to where you started. (I start directly in front of the flight path going towards the giant humanoid camp and follow the edges hitting all the veins. I crept past the elite dragons on the far-east side, a lot of Mithril veins sprout here.) At Tanaris, Mithril is mostly found along the south and southwest corners of the map, along with the insect lairs. One small thorium vein always spawns in the exact part of the southwest corner. (Not the ideal place for Mithril, but the second best)
     As for Thorium, Ungorro Crater is the best place (lower level mobs, and is shaped like a giant circle which is ideal for path mining). You must take time to search all the edges, the entire gorilla cave, the fiery mountain in the middle and the insect lair. Once gatherer has noted all these spots, set up a path for you to take, and do it over and over again. This should get you to 300 in a couple of hours if you are grinding from 230-250. But it depends on how well you can pave, because most of these veins are surrounded by 1-2 mobs.
Then come to Adamantite. People who have their flying mount will finally come to this. Nagrand is by far the best place to get this stuff by the handfulls. Just mount up. With 2 hours of farming you can have yourself another 200 Adamantite ore, and if you're a JC like me, that will bring you tons of blue gems within two hours! Of course this is for those with epic flyers. With the normal mount it might take you a bit longer. I predict 80 ore to every 2 hours if you don’t have epic mount. Just make sure to come here at night or even later, because this is a popular spot, and you will be granted more than 5 times for every 2 hours of farming
    Blades Edge is also a good spot if you need Adamantite. There are also a few spread out fell iron veins to be found here. This spot can be useful and great if Nagrand is currently being looted by Alli or horde at a high rate... I suggest that you come here if Nagrand is being mined like mad, as it will be sometimes.
I will not dwell on all the places for all ores. Finally remember the best place for Iron lies in the Hellfire Penninsula.