Really doesn't matter. Once you've opened up garage band, go to 'track' at the the top and select 'new basic track' from the drop down list. Then if you don't want to use the track that the top when you opened the new file, highlight that track and select 'track' again at the top and then 'Delete Track' from the drop down. Selecting 'new basic' gives you a track with nothing turned on, so you can get going pretty fast. Also, once you have your new basic track set the way you like it, go to the same spot and select 'duplicate Track' and it will give you another track with all the stuff that you put in your first track already there and ready to go. Finally, when laying down guitar, try recording your guitar parts twice. Record guitar in one track, the in a second track re record the exact same thing, trying to duplicate the exact same performance. Then pan each track hard left and hard right and it will make you guitar sound friggin 3D!!! Trim a little highs and lows with some EQ so the guitars aren't frighten with the bass frequencies to much and your on your way to some cool sounding riffage.