Interval Ear Training

A good place to start ear training is to learn to recognize intervals going up and down. Also, being able to think or sing the intervals is equally beneficial. An easy way to do this is to associate the first two notes of a song with each interval ascending and descending. It's important to choose a song that you're very familiar with, often kids songs or christmas carols work the best. Here's a list from wikipedia of possibilities but feel free to come up with your own.

It can take a lot of work to be really quick to recognize or produce music but I promise after practicing for an hour or so, you will be able to hear music much better.

Another trick I learned is to record a tape, cd, or mp3 of yourself playing a middle C and then playing 2 notes at random on an instrument (hopefully the 2 notes at the same time if possible) and repeating it with different combinations of notes. Then later going back and figuring what the 2 notes are by referring to the middle C you played at the start of each. This is great for your ear and once you're comfortable with it, start playing 3 or more notes.

I can't emphasize enough that this type of work is HARD but after a grueling session I promise you will be able to hear and enjoy music like never before.