This is a question I get alot. I teach music and when one of my students doesn't "get" how to read music, I get parents asking me this same question. My answer tends to vary for the person and how in depth they need to get. The basics of learning to read music are deceptively simple and once you get those basics down you will be able to do alot right away.

Basic Knowledge- If you want to be able to look at a peice of music and be able to read the notes and rhythms you have a quite a few options depending on how you learn best. Option one- get a learn to read music for dummies book and go through it (timing varies depending on your pacing). Option two- go to your local community college and take an intro to music theory class (very time consuming). Option three- take private lessons on piano or just on reading music (this will depend on your pacing and the skill of your teacher) Option four- have your 3-6th grade child enrolled in general music teach it to you (they should know and if they don't you better find out why- national music standards require this knowledge)

Applied Knowledge- You have one option. Start taking private music lessons and make sure you find a teacher who is focused on teaching how to read music correctly.

Detailed Knowledge- This is for someone who wants to understand it ALL when it comes to reading and looking at a peice of music. This choice is not for the feint hearted. You will need to do a couple of things. First you need to start taking those private lessons on your preferred instrument. Once you have it under your fingers, find your local community college and take ALL their music theory class in order. This will give the a knowledge level most professional musicians do not have.

Hope this was somewhat of a help to you and gives you an idea of what your options are. Good luck to you!