UC Davis is a large college, and most students need at least a bike to support their attendance for every class. You can find bikes everywhere in UC Davis, and here's suggestions of transportation ways.
Bike
Bike is the most popular transportation way in UC Davis. It's a good choice to buy a bike before the quarter starts. Bike can be bought through bike store in UC Davis (most expensive but convenient), stores like Walmart, and online (cheaper but inconvenient to get). The price may be range from $200 to $800, but it worth.
Remember to buy a locker for your bike! Stealing bikes often appears in UC Davis and it's hard to find once your bike is stolen! Better to buy a locker with a chain to lock your wheels as well. Wheels may also be stolen individually!
You can register your bike on UC Davis Transportation Services. It's not necessary, but it will improve security a little, and if you lose your key they can offer cut locker service. ($10 dollars for registration, and $150 for cutting a locker. So if you lose your key and still want your bike, just register your bike and ask for help.)
Remember to place your bike in a safe place if you are gonna leave it for over one week, like winter break. Thieves will stolen bikes that are left there for a long time. Longer it stays there, more possibility it gonna be stolen!
Bus
Bus is also a good transportation way, especially if you live out of the campus. You can search and view specific information on Unitrans - UC Davis website. You can also see the buses stop and bus information through map on your phone.
UC Davis buses are totally free to all the students. You just need to bring your student ID card and show it to the driver. It can bring you to housing estate nearby and stores like Target and Safeway.
Scooter
More expensive, but more convenient choice compared to bikes. However you cannot register a scooter in UC Davis Transportation Services for now.
Same suggestion as bikes, scooters are also target of theives, so be careful.