Choosing a bass guitar is a similar process in many respects to choosing a regular guitar. The first decision you will need to make is whether you want an electric or an acoustic bass. An electric bass guitar must be plugged into an amplifier so sound can be heard properly, while an acoustic version features a hollow body that amplifies the sound without use of an electric amplifier. Once you have decided which sound suits you, consider your playing ability and budget to narrow down your search.
Beginners will benefit from a less expensive bass guitar that is specifically designed for their playing abilities. This usually means a shorter, narrower, and thinner neck that will make playing much easier. More advanced players will want to consider a wider and longer neck that allows for more notes to be played along the fret board. More advanced players will also need to pay attention to the distance between the nut at the headstock and the bridge; this will increase the playable scales, and it will also usually increase the distance between frets, which are the metal wires on the neck that create different intonations when the string is pressed against them.
Two general body styles of bass guitar exist: a neck-through body and a bolt-on neck. The bolt-on neck features, unsurprisingly, a neck that bolts onto the main body of the guitar. The neck-through body features one solid piece from the neck down through the body, and the body is then expanded or otherwise formed with additional pieces of wood secured to the neck. Choosing between the two is largely a matter of preference. The best bass guitar in this case will depend on your playing style: a neck-through design tends to be warm and consistent, while a bolt-on neck bass guitar will be punchier but less consistent in tonality.
The tuning machines are the devices located on the headstock, or top of the guitar, that hold the strings in place. Choosing quality tuning machines extremely important, as low-quality machines will be far less likely to keep the guitar in tune while playing. Be sure to ask a pro at l local music shop to give you some insight as to the design and brand of tuning machine that will ensure the best sound.