Decide on how you wish to dole out songwriting credits. Many bands, such as Van Halen, have opted for a unified approach, meaning that no matter how many notes a certain member came up with, all members receive equal credit and royalties. While this eliminates arguments in the meantime, it should be noted that various members may have different opinions as to how to use the song in the future. For example, if a car company wants to use your song, and the other members are for it but you aren't, it can get complicated. Also, if you are a songwriter composing for performers, you should make it clear what percent you want - 50 percent is the standard rate.
Select a permanent formula for figuring out who gets credit for what - if you have chosen not to go with the equal songwriting credit method. It's best to have a set method and not change it, lest others in the band try to manipulate the process to get more money. For example, you may want to have a system where the lyricist and main music idea writer are the only ones credited, regardless of whether or not the bassist wrote an intro or a bridge.
Pay attention to your contract. Mechanical royalties, or PA copyrights, are monies received for your content that can be reproduced. They either are, or will be the bulk of your income, but the rates vary. You stand to earn more if you write, record and publish the music yourself, which has often been the norm. For example, if an artist doesn't own their own publishing company, they will still receive a royalty check thanks to the sound recording copyright, but some of the money will also go to the owner of the PA copywright.