I've been playing for 15-16 years now. When I was in high school, myself and all my other axe-grinding friends could only play sitting down. As you get better, at least half your practising should be done standing up(infront of a mirror also helps) and eventually, you'll be able to play much better standing up. Infact, for jamming, not practising, you'll find that the freedom in not being glued to a chair and the ability to move around will allow you to play much better. Also, the biggest mistake that people make is playing with their guitar way too low on the strap. Too many axe players I see live really suck because they can't reach notes on their axe and they have no control with the instrument because their guitar is down around their knees. It's always way better to play great than look cool and suck musically. Any great axe players that I've seen live, up close and personal, all have one thing in common. Their guitars are just an extension of their body rather than a hunk of wood that they wear. When I saw Stevie Ray Vaughn at The El Mocambo in Toronto a week after Texas Flood was released, his guitar was like another appendage, an extension of his body. It moved with him rather than him having to make it move. The guitar was in perfect rhythm, sync and harmony with his body because it WAS part of his body. The only other person I've seen live, up close and personal who really actually "dances" with their guitar is Jimmy Page. He breaks all the rules though as his guitar is slung low down around his knees, but since everyones' body proportions are different, he is the exception rather than the rule. Jimmy was once described as "a T.V. antenna with legs" for a picture of him holding up his doubleneck guitar. That's because his instrument flows with his movements. When I played my first band gig about three years ago(also at The El Mocambo), I was totally amazed and surprised how loose and comfy I was playing, way more loose than I am in general when I talk to people in the office etc. Finally, you must be rehearsed and know the songs inside out because anyone who gets lost during a song or doesn't know which scale(s) they're playing from during a solo will be as stiff as a board. Sorry for "Rambling On" but this is a very personal topic. Roy Buchanan was definately the greatest guitar player I've seen live(sorry, but also at the El Mocambo)who didn't move around at all. Instead, he made faces and grimaced as he palyed his guitar. His guitar was always very high on his body with the bottom around belt buckle height. He just didn't have to move to express himself as did
the other players that I mentioned.
The bottomline is, don't move around if you have to plan it out or force youself, you'll look really unnatural. Let your fingers do the talking and you'll be just fine.
Imagine tryin' to be smooth and cool wailin' your arms around beatin' on the skins ahvin to sit around all day during the concert. 