Well, yes it's very important to write down your ideas, and it does make things easier when sharing with friends. However, I think that as bandmates, you guys should be willing to listen each other... we don't always have time to write certain ideas down and it's important to be able to translate these ideas through casual communication. And sometimes your friends can offer some input of their own, whenever I write a song I feel that nothing is ever set in stone, I'm always searching for improvement.

I had this band in high school, and when our singer bailed on us at the last minute, I asked my gf to fill in for him. Now we've always been able to translate ideas to one another (in more ways than one) :) but at the time she was a little nervous when I was going over the arrangements. So being that we had so much time before show time, she chose to improvize.

Sometimes it can be too much of a hassle to learn some one elses songs note by note, so we sometimes take what we will, and then add our own creativity. Don't be afraid to listen to each other, and if you guys have the patience, don't worry about how long it takes, as long as you're all happy with the songs final take.

Good luck!