There are many things that could go wrong when starting a band that can stop any progress right in it's tracks! If you are the one starting a band, it's up to you to plan out how to effectively take your band from thought to reality.
Pick A Genre And/Or Style
Before you start a band, make it clear in your head what kind of music you want to make. Be very specific of the sound you wish to create. The last thing you want is a band who's songs don't sound well together. You want to start with a finished product in mind, not start and see where it heads.
The Song-Writing Process
I've gotten into many arguments with other musicians over the years during the songwriting process. It's a common thing, but also something that could have been avoided. When you first start a band, it's best to write a few songs yourself or with one other person, rather than a whole group. This way, your sound will be focused and any members that join you later will know what exactly what style and sound they are contributing too. If you have the whole band write songs from the beginning, you and the other musicians might have conflicts on what the sound of the band should be and it could end up stopping the band altogether.
Getting Members In Your Band
It's important that you pick the right people to make music with. Music should always be enjoyable, but it also is work and you need members who are as dedicated as you are. Don't settle, there are many great musicians out there who would love to be involved in a band.
I would stay away from musicians that are far below your abilities, even if they can play the parts. I find that generally they can't keep up and it just slows down the writing process and the progress of the band.
I would also stay away from musicians who far exceed your abilities. Often they try to take the band in the direction that they want, for better or for worse. Remember that if you started this band, you want musicians who want to contribute and work with your idea, you don't want members who want to change it.
This is not to say they're arent exceptions, but in my experience it's best work with people who are around your level of musicianship.
Once the ball gets rolling, a band can really work great together and accomplish a lot. It's amazing to see your musical idea come to life. Performing shows, recording, and writing songs only gets easier and more fun, and this is why you want it's so important to make the right decisions when first starting a band.