Invest in a metronome.
Start the metronome at a speed you can comfortably play at, then gradually increase it.
Focus on playing accurately and properly, don't rush to a higher speed if you're sacrificing quality.
Speed will come from your muscle memory strengthening.
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The advice is: Do not focus on playing fast.
Focus on playing expressive!
Joe Satriani said (I can't find the exact quote, this is how I remember it): There are very many players that have a good technique.
They play very fast, their fingers stretch very good.
But very few of them know how to be expressive - and that is the most important thing.
But, if you still want to play very fast (shred), you should checkout Michel Angelo's DVD " Speed Kills ":
I think this is the best material there is.
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Play with a metronome, while you are practicing drills.
It's nice to be fast
but it's really important to play in time.
Once you get a speed in beats per minute where you are comfortable and are playing smoothly and cleanly then you you start bumping up the speed on the metronome a little at a time each time practicing until you are clean and smooth at the speed.
In my opinion and if you watch a video of John Petrucci playing
it's really apparent,
how cleanly and smoothly you you learn to play at lower speeds will determine how fast you are at higher speeds.
It's all about efficient movements of your hands.
It also helps to video tape your hands while playing and watch for wasted movements, the less you have to move you fingers
/hands the faster you will play.
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Speaking of a certain solo you want to speed up; Do not use metronome until it %100 gets into your muscle memory
and you can play perfectly and expressively in slow tempo(or No-Tempo)
Until then just play slow and "FOCUS" on your right and left hands watch if there is any uneconomic excessive movements, the angle you hold the pick, how much of the pick is flapping outside..
etc.
The more you focus on anything the more experience will be permanent.
While focusing, spot and constantly eliminate any muscle tension in your arms and hands(this is HUGE)
Your goal is to have an incredible lightness in your fingers.
If you feel exhaustment or pain in your fingers after a small solo, chances are you are playing against a lot of muscle tension, which can lead to injury and limit your speed.
(don't confuse this with the mellow tiredness of a muscle group after a workout
) "Listen" the sound you create, make it sound flowing and "BEAUTIFUL" in any speed, as if even with that speed it would play on radio and people would love it.
Every note should have a definition.
When it starts to sound "beautiful" and correct, then preferably with a metronome little by little increase the speed without compromising that beauty and quality.
But speed should come to you as a result of excellent conditions, and not you are trying so hard for it.
All of a sudden you will feel like you can play a little faster with any extra efforts and tensions.
Then you never have fear of playing the solo right or wrong for that speed, it will always be right.
it will not be one big moment in the song that you feel the fear before solo if your gonna pull it correctly now or not.
Then you will get stuck on certain parts of solo, analyze them whats going on(which picking mechanics
you use(up/down), are you changing strings with an up or down stroke ..etc) and isolate and only work on that 2-3 note spots maybe 1000 times(this is called efficient practising)
then slowly incorporate everything together by the time.
After a while you will be saying to yourself "
It's so easy, how come I couldn't play like this on the first time"
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There is this pc program that helps you do
just that check it out:
http://www.guitarspeed.com/ note: I am not spaming in any way nor affiliated to this site.
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I've seen people like  John Petrucci  playing incredibly fast with their right and left hands, but I can't seem to get any faster than I am now (which is speedy, but not near as fast as John).  Is there a technique I can use to increase my alternate picking speed? What about my fretting speed?  Edit: I have heard of "circular picking" and picking with just your thumb and index finger. Are either of these better for playing with speed?
How do I improve my picking and fretting speed?
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<guitar><electric-guitar><technique>
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music.stackexchange.com/users/82/Mike Webb
Improving picking and fretting speed takes time and practice. Start by playing with a metronome, while you are practicing drills. Start the metronome at a speed you can comfortably play at, then gradually increase it. Once you get a speed in beats per minute where you are comfortable and are playing smoothly and cleanly then you you start bumping up the speed on the metronome a little at a time each time practicing until you are clean and smooth at the speed. It's all about efficient movements of your hands.  Your goal is to have an incredible lightness in your fingers. Speed will come from your muscle memory strengthening. Using a metronome is good to build speed. Aim for efficient and light movements without tension. Speed will come as your muscle memory strengthens.
Using a metronome is good to build speed. Aim for efficient and light movements without tension. Speed will come as your muscle memory strengthens.