You won't have fans at your earliest shows; you'll have friends supporting you. This is crucial for your early shows. You need to show the clubs that you can get a crowd out. The clubs don't care if the 50 people you bring out all live on your dorm floor or if they're long time fans and own your entire discography. 50 tickets is 50 tickets.
The trick is to move from a friend-based crowd to a fan-based crowd. This is a slow process and you most likely won't have a definitive moment where this transition happens. One day, you'll look out and realize you don't recognize the majority of the people in the room. That's when you've achieved the next level.
There's no easy way to get here. Because you want to get people out to every show, you'll want to bombard your friends with show invites. You have to be smart about which shows you tell people to come to and make sure you space out your important local shows. You can't expect your friends to come to every show especially if you're playing multiple times a month.
Each show should be unique. If you're playing a club on campus then invite just your friends who go to the college or live near by. If you're playing a club downtown then invite those you know typically head downtown. If you're playing a club where you need to prove to the booker that you can bring a crowd then invite everyone and push this hard.
It's tempting to invite everyone you know to every show, but this will burn out your friends and eventually none of them will come to any show.
Facebook isn't everything. If you haven't noticed yet, Facebook events are not the best at gathering accurate numbers of who is coming or not. This is especially true with concerts. Don't invite every friend to every show. I learned this the hard way. I used to invite every single Facebook friend to every single show I had anywhere in the country. I thought "well even if they don't live anywhere near this place they may have friends that do and they can tell them about it." This is a nice thought and may work sometimes, but if you are in the stage where you really rely on friends coming out to shows, rally everyone up around one show every two months or so. It's better to have 75 friends at one show than 10 different friends at 10 shows. +It Doesn't Take A Web Genius
If your friends enjoy seeing you they'll happily come out more often and will go to your website or Facebook page and find out when you're playing next and show up even if you don't personally invite them. However, if you invite them to every single show they'll most likely never come out because they will get annoyed with all the requests or they'll think that because you play so often they'll just catch the next one.