Comment by analog31

This is a general tip that goes beyond pitch and intervals: Learn to sing things that you play and hear. This is good for a lot of things. It's a way of developing your ear without the mechanics of your instrument getting in the way when you're starting out. You can "practice" when you don't have access to your instrument, even listening to the radio in your car. It will develop recognition of familiar musical patterns.

You can practice singing the intervals. What's a fifth sound like? You should be able to sing it. Or play it on your instrument and then sing it.