My band's name is Greece and we're starting rehearsals, tomorrow. How long would you advise me to simply jam, because I'm scheduling a show in a few weeks on December 12th. What is your advice for rehearsal?
dont plan a show before you atleast have one practice... cuz some people might all be good but just dont fit together
A few weeks is actually two months from now.

What kind of show, birthday party, local gig?
Quote by SOADrox429
'Bring me the still-beating heart of a newborn child, and the world's rivers shall run red with the blood of the innocent.'

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planning a show in the early stages can actually be a good idea to get members motivated. That's what my last band did but then again we broke up anyways jam as much as possible!
To be honest, you shouldn't be booking any shows until you have at least a viable set rehearsed.
Otherwise, you stand a very real chance of letting a lot of people down.

When you book a show, it's kinda like a 'promise' or a verbal contract.

First of all you promise that you are in a position to book a show, then you are promising that your band have the means and capacity to play that show.

At the moment, you have neither.
Get rehearsing, get a set together, get the set tight, then think about booking gigs. Otherwise, you could find that after your first show you will have to change your name just to get people to come and see you a second time.
In a gigging band, your reputation is EVERYTHING, so if your first gig is so bad that it ruins your reputation rather than building a good reputation, then that's a step in completely the wrong direction.
So it's not really something that you should be booking now and hoping that you'll all be fine by the time the gig comes around.