Knowing when you're ready to join a group?

Ive been playing for awhile..But Ive yet to really play with others or a group....Back in the day I use to play open mics with a buddy of mine but they were nothing serious...

Basically, what should one know or should know or can do...to join a group of fellow players...

I know some people who just lost there sax player, Ive been thinking about asking to join in on a band practice or see if they want to add another guitar to there group..

er, well, I don't personally think that there is any set level of technical command and knowledge needed to be able to join a band to play music. Having CONFIDENCE is the biggest thing I think. You may not be the greatest lead player of all time, but if you are comfortable with playing leads while other people jam to back you up, I think that you are ready to join a band to make music. There's people that have been playing for maybe only a year that are starting up bands of their own! haha

My old drummer was absolutely terrible, but we never told him that. He just lacked any sort of real confidence in his abilities, which furthered the fact that he never did anything to improve himself. So he didn't last long.

Be confident in your abilities, and always want to improve. Those are the two biggest parts of joining a group.
...for me.

But it wouldn't hurt to ask if you can jam a few songs with them to see if they would like another guitar ^^

You're ready ... when you're ready.

I mean, why does there have to be a certain set skill level or playing ability to join a group? Music really ought to be about enjoyment and so just try it out and see what happens! The worst thing that happens is a group says no to you and then you are just where you are right now, it's not like you lost anything. Give it a shot!