Just like athletes, guitarists are prone to various pains and even injuries that many times can be avoided by properly warming up. I'm going to tell you exactly the kinds of things I use to warm up before practicing or performing every day.
My goal when warming up before practice is to be able to comfortably play those things that I know well and feel are a solid part of my technique. That way, I feel confident when learning a new section or exercise that I haven't mastered yet. I usually break warm up exercises down into either being primarily for the right hand (picking technique) or for the left ( chording, scales, etc...). My personal weakness is my right hand technique, so I usually try to do as much alternate picking type stuff as possible. Always start slow. For alternate picking we are strictly down up picking all parts. I usually will play a chromatic scale type pattern or something were I'm playing four notes per string. These exercises will keep your left hand fingers close to the fretboard, making your finger movements as efficient as possible. Also, we are using all four fingers on the left hand equally. Yes, even the pinky. At the same time you're right hand will be moving in a consistent down up, down up motion.
Before going forward, let me just mention that these are the things I use to warm up. If you use directional picking, like economy picking or sweep picking, you will want to of course use exercises that incorporate those techniques. The same logic would apply to finger picking. If you're a classical guitarist, most teachers will have very specific advice on how to warm up. Some things are universal, so again, start slowly, concentrate on proper hand position and then increase your speed.
I spend a fair amount of time every week teaching private guitar lessons. What happens a lot of times is I have a guitar in my hands and I'm doing a lot of teaching, but not so much actual guitar playing. In these situations, I try to take advantage of breaks between students. Even if I only play for ten minutes or so, I feel "warmed up" when the next student arrives. The same situation at a band practice, turn down your volume and stay warmed up by practicing while other musicians work out their parts or while your drummer tries to position his toms "just right". Be courteous and remember, no one likes a noodler.
Another thing I like to use for right hand warm up is funk playing. Keep it simple with the left hand so you can concentrate on keeping the right hand relaxed and in constant motion. Playing a D9 chord is a great place to start. Mixing things up like this keeps your warm up fun and you'll be learning something new.
I don't really consider myself a "jazz guitarist", but I love jazz chording. I have a couple of really cool exercises that I've come up with over the years that make great warm up exercises. One of these is a diatonic chord "scale" which uses all chords played on the same string set. 5, 3, 2, 1 ( A, G, B and high E ). This is a great way to increase muscle memory in left hand and increase your chord vocabulary at the same time. I usually play this with my fingers (right hand) as opposed to a pick. The thumb plays all notes on the A string and the other three strings are played with the index, middle and ring fingers.
This is an excerpt from an article by guitarist Bill Havens