To record bass guitar is not something the newbie recording engineer can capture easily. It can get too loud or too soft or it can even get boomy or squashed. This kind of instrument requires a delicate touch and I intend to lay out some ground rules to make your job easier.

Get your levels set first. There's nothing worse than recording a great bass performance only to have it clipping the input meters. Sometimes you can mend a peaking track, but I wouldn't recommend it unless you are absolutely stuck with it.

Look at the rest of the mix. This may seem backwards, but you need to "clean house" so to speak with the rest of the mix. I've worked on tons of projects over the years and I've picked up some invaluable tips working with other producers and engineers. Setup a highpass filter for all your other tracks to cut out all the frequencies below 100Hz (some guys have told me 200Hz, but you do what sounds best to you). What this does it clean out the sonic territory down there where the bass guitar resides. The one exception to this rule is the kick drum.

Use an analog overdrive pedal. Most experienced engineers use some sort of overdrive when recording bass guitar. Even in a pop or soft rock setting, overdrive will fatten and level out your bass guitar's natural sound. Overdrive - more specifically tube overdrive - occurs when the sound is distorted and pushed beyond it's normal sound wave. When this happens with a vaccuum tube, the sound wave is distorted in a way that is pleasing to the ear. This effect also introduces a fair amount of compression to the signal and thus evens out the loud and soft parts of the bass track. A bass guitar can be terribly uneven and hard to control even with the best studio players. I've used several pedals to achieve a solid bass overdrive including these two favorites:

Don't be afraid to use a healthy amount of compression. Using effects can sometimes color the sound in a bad way. Other times, a good use of an effect like compression can also smooth out the track and help it mesh with the rest of the track.

Try recording your bass through a DI (direct injection) and a mic'd bass cab simultaneously. Paul McCartney prefers his bass recorded with a mic'd up cab - BUT, just because a legend like McCartney does it this way doesn't mean they all do it. Regardless of how you like perfer to record your bass guitar tracks, it's worth a shot to try both at the same time. Some guys swear by running the bass straight into the board/mixer. Others will only mic a real bass cab (typically crank'd up real loud). I say mix a little of both. It gives you the best of both worlds and allows you mix the exact tone and shape it accordingly.

Bottom Line - Clean up your mix, smooth out the bass with overdrive and compression, and don't be afraid try different techniques.