There we go, my view on how you should practise your music.
This is the stuff that helped me get into Amsterdam School of Music (which I later turned down to study Mechanical Engineering:P). In no particular order:
1. Take lessons from an experienced teacher. Someone that can show you proper technique, theory (including scales, reading, rhythm, chords, etc.) , musicality, the works.
2. Practise songs you like. This will motivate you to practise more and get better.
3. Learn to (sight)read both bass clef AND treble clef. For advanced musicians; learn the C clef (or whatever you call it).
4. Get a rhythm book; this is a book with all kinds of rhythms on a stave that you have to tap with your hands, one hand the sign, the other the beat. example:

So with your left hand you tap 1 2 3 4 on the beat. Your right hand taps the actual rhythm. START OUT EASY. Coordination gets tricky if you rush it.
5. Sing your lines so you know what they sound like, the biggest problem is often not how they sound, but how they should sound. For advanced musicians; sing new lines BEFORE you play them.
6. Get a metronome. Yes, I said it. Get one, now! Play simple grooves to your metronome at first. Later play known lines to the metronome and finally play unknown lines (sightread) to the metronome.
7. Practise a good half hour straight a day, then take a break, to continue if you wish. Start your practice with playing stuff you already know and like, then continue onto scales, chords, whatever your assignment was from class, then proceed to songs you need to learn.
8. Break down your songs/lines according to theory. Look at the staves, what do they actually say, and more importantly, why? Why is that note an F# instead of a Gb? And why are you playing in Amin instead of Cmaj?
9. Learn how to recognize chords, scales, intervals and rhythms by ear. You can do this with a handy program like this one:
http://www.solfege.org/Solfege/Download
10. Have fun while playing! I can't stress this enough, if you're not enjoying yourself while you're playing a song you like, you won't get better. Also, no one ever said scales should be fun.
Optional: get special theory (solfege) lessons if available in your region. They teach you the lingo and stuff you need to know for any instrument, ranging from circle of fifths and how to apply it to sightreading, tapping rhythms and writing down chords to a line.
Enjoy playing!