Have you started playing World of Warcraft, chosen which type of weapon that you wanted to use and only stuck with that type of weapon? I have, and if you decide later on that you want to learn to use a different type of weapon, raising your skill in the new branch can be a hassle. Here are some tips about learning new weapons.
There are many different weapon groups for you to train in and the trainers for different types of weapons are scattered amongst the major cities for Alliance or Horde. The weapon trainer in your home (major) city will tell you where you can train for weapons that they don't offer. Be aware that some classes cannot use certain types of weapons.
Let's say that you have a rogue who specializes in daggers but then you decide to "spec" in combat. This is not an ideal weapon/spec combination.
If your heart is set on backstabbing your enemies then you will need a dagger in your main hand. Mutilation may be a better spec for that. For a combat spec though, a slower weapon that has higher critical damage is a better option than a dagger that has faster attack but lower damage. By lower damage I mean overall attack damage, not to be confused with damage per second (DPS). The reason a slower and higher attack weapon is better is that you get much better damage by using the special attacks that the combat spec uses. So now you need to learn different weapon classes.
Using the example above...A good solution would be to keep your dagger in your main hand and put a sword, mace or fist weapon in your off hand. You can begin to raise that weapon skill in your off hand regardless of what level your World of Warcraft character is. Once you get that skill raised to a comfortable weapon skill level for your character level (level x 5), then you can put it in your main hand and go from there. If you need to raise another weapon skill, rinse and repeat. If you are getting beat up badly because you are not connecting with your unskilled, off hand weapon, keep your bag open that has another weapon in which you are more skilled and switch weapons in the middle of the fight. Regain your health after the fight and start over with your "bad" weapon.
Using this method you will be able to max your weapon skills quickly. I never used a one hand mace on my rogue until level 76 (sad, I know) but was maxed out within a level or two. Using this method my rogue is now equally skilled in daggers, one hand swords, one hand maces and fist weapons, (which shows as unarmed skill). Also, throwing but that is a different issue. This will work for all melee classes.
There is an achievement for mastering four different weapons. Typically you can get all four weapon types skilled up each level. If you are still a point or two away from your max by the time you "ding", don't sweat it because you will raise skills quickly when starting a new level.
So even if you are completely unskilled in a weapon, don't let that stop you from getting your achievement and being versatile enough to be proficient in several weapon types because you just never know when a great item will drop in an instanced dungeon. That is one of the perks of World of Warcraft, the unknown.