Take music lessons
This is a bit of a given, but it's still an important reminder. Getting lessons with a good teacher will allow you to learn any instrument faster and more efficiently. Having somebody to guide you and show you how to avoid bad habits early on will save you a lot of backpedaling and relearning down the road. If you have a friend who plays the instrument you’re trying to learn, you can always ask to trade lessons with him or her; your friend will give you a lesson on your new instrument in exchange for you giving him or her a lesson on your primary instrument. There are ways to make it work – and it is so, so worth it!
(Resources from the web)