Bass Guitar is very hard to mix. It is always the main reason why the mix sounds either dull, thin or mud. The major problem is that all instruments have bass frequencies, but not so heavy as bass guitar and a kick drum. In a mix, all instruments are played together and the primary problem lies in the bass frequencies, it is why every time you heard tracks that are not mix, it sounds mud.
I have been mixing for years and I love to present these two techniques I learned from experience in mixing. Basically you can only apply one technique per song. But you will have two choices how to approach mixing bass guitar in the mix :
a. The Rock Bass Guitar Sound Mix - in this mix, the objective of the bass guitar is to sound heavy and partly dominant in the mix. As a rock producer, I like the bass guitar to sound aggressive and up front in the mix. Did you notice that once you hear rock tracks today such as Trapt, Green day, Simple Plan, their bass guitar is very dominant? It is a secret of sound engineers in how to make bass guitar loud while avoiding mud.
As a guide, we will designate 45 Hz to 250 Hz as the bass frequencies where kick drums and bass guitar mainly reside. The problem is how to blend those two together.

Since the bass guitar needs to sound heavy and dominant, it should occupy mainly the bottom 45 Hz to 250 Hz. But….
We will dip 100 Hz for the kick drum spikes to shine through. I usually dip the bass guitar around 100 Hz with Q settings of around 2.0 and -9dB reduction.
To balance, I will boost kick drum at around 100 Hz with Q settings of around 2.0 and 9dB~12 boost.
To sound better, I will apply high pass filter (so it will attenuate frequencies lower than 50Hz) on kick drum around 50 Hz -3dB reduction, for the deep bass guitar frequencies to dominate the sub woofer, making it sound heavy.
But I will not apply boosting to bass guitar at any frequencies between 45Hz and 200 Hz.
I finally boost 250 Hz for bass guitar to make those notes more