The biggest thing that holds any guitarist back from being the fiery soloist they imagine in their head is fear.  Your brain gets in the way of what your hands want to do.  Use these tips to help your loosen up, get over the fear, shove your brain aside, and get to making great music.

1. Has anyone ever been killed by a bad note?  No, of course not.  You can't kill anyone with music unless you physically beat them over the head with your instrument.  So, aside from some punk rock shows I've been to, music is a safe game.  Human nature makes us want to fix our mistakes.  But when playing music you have to train yourself to not worry about mistakes.  There's two reasons for this.

First of all, second-guessing what your playing, as your playing it, will slow the whole process down until it grinds to a halt and you give up on the solo.  Creators in all art forms have learned that you have to turn off your internal critic and just create during the first draft.  And improvising is that throwing that first draft out there for better or worse.  Just ride it.

Second, you never know what cool musical discoveries you'll make in the form of a mistake.  Years ago I was trying to cop a drum loop from a particular song so I could see how it was put together.  I hit a wrong button on my drum machine and it created a different loop.  I got inspired to write a song around that mistake loop.  That song has been featured in five movies since.  Mistakes can be awesome.

If you play a bad note see if it has any value.  If not, just forget it and keep going.

2. Start by playing anything.  Jazz players call this "free playing" and it's a great way to get through the mental endurance roadblocks of improvising.  Do not over think anything while doing this exercise.  Don't worry about playing over chord changes or even in a particular rhythm or tempo.  Set a time for two minutes.  Start creating melodies on your guitar without stopping for the entire two minutes.  Again, don't think, just play.  Whether it sounds good or not isn't important here.  You'll be training your brain to stay out of the way while you create spontaneously.

3. Give yourself strict constraints on what you play.  This is the opposite from the previous tip, but it's used for a different reason.  This will help you think in small groups of note and rhythms to create concise, memorable melodies.  It also helps you to really dig out every possible idea from an area.  Here are a couple of examples:
- A two-chord groove of one bar each and you can only use the top three strings of a pentatonic minor scale.
- A one-chord groove and you can only play major scales on the first string.
- Play through a whole twelve bar blues chorus using only one note. (This is one of my favorites)

In reality, you can play any note over any chord at any time as long as you like the sound of it.  There is a music theory explanation for even the weirdest sounding stuff.  However, going in with that mindset is to general to help as a beginner guitarist.  It's like saying, "Go walk somewhere." It's much more helpful to say, "Walk to the Valero gas station at 2nd St and Main."  Constraints will teach you how to form interesting melodies that can then be expanded out into the crazy stuff.

4. I have saved my own behind in more onstage scrapes than I can count with this one trick.  If you hit a note that sounds weird during your improvised solo, but you know you're still in the right scale pattern, go one scale tone in either direction and you'll end up on a note that fits the chord better.

If you accidentally slip outside your scale pattern and end up on a weird note, just go one fret in either direction and you'll hit a note that works better.  Remember that: You're never more than one fret away from a note that works.  You'll get yourself back on track and you'll get the bonus of looking like you made a cool "outside" move in your melody.  Really.  I've pulled this off in front of audiences full of experience guitarists and came off looking cool instead of like a dope.

5. If you can look cool by using trick #4, why not start making those kinds of mistakes on purpose?  Exactly my point.  Go back to #1 and #2 and start making the weird notes work for you.

If you work through these ideas you'll free your brain from worrying about what to play next and let your fingers and ears find amazing ideas you wouldn't have thought of otherwise.