How To Practice Scales
The first stage of any scale practice routine needs to be to memorise the scale. As stressed in other parts of this site it is important that you learn one scale well before moving onto more positions.
Using a routine like the one outlined below is good for breaking out of scalular playing. It is ironic that we spend a lot of time learning scales and then spend a longer time making sure it doesn't sound like we are playing scales :)
All this is discussed in greater detail in my DVD Master The Major Scale where you also learn cool ways to use them in improvisations!
Five Stage Scale Practice Routine
Before you start practising the scale, you need to learn it from memory. Do this slowly and carefully and be sure to get it perfectly clear in your mind.
Stage 1. Up And Down
The first stage should be to be able to "cycle" the scale - that is to play it up and down over and over without stopping. This should be done with a metronome at a speed comfortable to you to be sure that the timing is even. Also to focus on the volume of the notes that you play and try to keep it consistent. Be able to play the scale 4 times perfectly, without stopping before you move on or move the tempo up.
Stage 2. Random Direction Changes
Once you can cycle the scale it is time to start changing direction at random. Start this slower than your speed for stage 1 and make sure that you play continuously. Don't pause, stop or start soloing (going off on one...). Try and stick to it being scalular - don't skip notes and always play notes next to each other.
Stage 3. Random Notes
Now it is time to explore the scale. Play random notes from the scale, be very careful to ONLY play notes from the scale. Play it slowly and get it right. It is easy to rush this one and make mistakes. DON'T MAKE MISTAKES. Ever. There is no point in practising the wrong thing. Keep the notes evenly timed, explore skipping strings, jumping from very low to very high, generally explore the scale. You will find that this really tests your knowledge of the scale shape. It's not music yet - it's exploring - don't get them confused.
Stage 4. Play in 3rd's
As you may know, chords are built up in intervals of a 3rd. This means that by playing notes that are a 3rd apart they will tend to sound good together. Often melodies use chord tones, so after some time practising this pattern, your improvising should start sounding more melodic. You can think of 3rds as playing a note, then missing the next scale step and playing the next. Then go back to the note you missed, and go up a third again (skip a note). This is a great exercise and I would highly recommend spending a good amount of time on this exercise and getting it really solid, so that it will come out naturally, without you having to think about it.
Stage 5. Four In A Line
Another good pattern to get down is called four in a line. Start on the first note of the scale and play up four notes. Then start on the second note and play up four notes again. Continue this pattern up the scale and then back down. This is a good way of developing a "way out" of a scale because you are playing four notes of a scale and then skipping.
Stage 6. Use It
Then get using it... find some appropriate backing tracks and start experimenting with it. For Pentatonic scales, you will need to get into learning licks, for The Major Scale you need to get into ReActive Listening and finding melodies that work over the chord (and learn some licks too!).
Most important is not to forget that a scales is just a tool to HELP YOU MAKE MUSIC! I recommend forgetting about playing them fast or fancy - work on using them to express musical ideas and corny as it sounds, express your feelings! That's really what it's all about!