Do Your Research
Use the many web resources at your disposal like WowHead and WowWiki to fully learn the layout of each dungeon and the strategies involved to defeat each of the enemy encounters. This is especially important if you are tanking, as you’re expected to act as the leader of the group and should definitely know what you are doing.
Use An In-Game Guide
If you’re tired of having to use sources outside of the game to master dungeons then you might want to look into getting an in-game guide. These are guides you can use while playing the game that respond to your actions and can show you exactly where to go and what to do. One of the most popular guides on the market for this would be Zygor’s Dungeon and Gear guide. It not only gives you all of the information you would normally have to scour sites for hours to get, but it also has tools that actually find the best weapons and armor for your character and tell you what dungeons you need to run in order to get that gear.
Make Sure You’re Well Specced and Geared
You will want to make sure your character is properly specced to handle whatever role you intend to play in the group and that your character is outfitted with the best gear possible. There’s nothing that irritates other players more than when a player is undergeared and it keeps getting the group killed.