InstrumentThis isn't exactly a secret, but having a great bass will immensely contribute to a great bass recording. It is not completely necessary, but having awesome pickups on an awesome bass is a great combo for success. Also having the bass setup properly will keep it in tune no matter which frets you are playing. Before going into the studio, it is crucial to always put on fresh strings as well. If you don't put on fresh strings and you have really nice pickups, they are only going to pick up the bad strings better. And if you have a cheap bass, the easiest way to make it sound more better is fresh strings. This is where the sound starts. If this sounds bad, you can't save it in the mix. Spend most of your time getting this right and everything else will come much more easily.
Split SignalAfter the bass itself sounds really good, it's time to record. One of our favorite methods is to split the signal. One ends up going to a DI and the other can be sent to an amp. The two can then be affected separately in the mix. For passive bass DI, we love the Radial Pro DI because these metal boxes are built to last and sound great. For bass amps, we love the Hartke HD series for their hybrid speaker. This delivers a really punchy sound and very crisp highs.
Cater to Your Style
Some types of music require you to strum with force, some require a very delicate touch. Really listen to the sound coming out of your amp and make sure that how you're playing the bass is producing the best tone possible. Strumming by the neck pickup vs strumming by the bridge makes an enormous difference in tone. How hard you hit the string also has a huge impact on the tone. Bass is more susceptible to this than any other instrument. Simply moving your hand from the neck pickup to the bridge pickup can make your tone go from round and flabby, to tight and defined.
Also, choosing to finger pick vs using a pick has an enormous impact on the sound. Listen to the tone and play to the sound. It is very possible to alter what is happening quite a lot just with a small change in technique.