Well the main part of making a band is finding people to play with.
Guitarists - a dime a dozen
Good Guitarists - 1 out of 50
Bass players - 1 out of 50
Good Bass players - 1 out of 100
Drummers 1 out of 25
Good Drummers 1 out of 50
Of cousre these are just rough stats on how easy it is to find musicians for your basic plain vanilla garage band. You can have a band with none of these instruments if you want. Prolly be more interesting to see too.
But anyway, finding people to play with is step 1. Chances are you already know at least 2 guitarists and a guy that doesn't know to play but is willing to learn how to play bass in your band.
Next find a place to play. If you still live with your perants then your golden. Take advantage of the garage. It will be your sanctuary. I practially lived in my parents garage throughout junior high and high school playing my drums. Now that garage is something I dearly dearly miss
. If you don't live with your parents but have your own house then go for it. Hopefully your roomates and neighbors will be cool. If not you may have to rent a rehersal space to jam in. They usually run somewhere around 30 to 50 bucks for about three hours depending on where you live. Not free like the garage but at least it will have air conditioning (most likely).
The next step would be to play. Regularly. Like once or twice a week minimum as a group. The songs will come the more comfortable you get playing with your band. So much so that you shouldn't even have to force it.
That's all I can think of right now. Bottom line is playing in a band is a lot of work but well worth it.