The low end is a delicate part of the spectrum and must be considered, processed and mixed correctly. Instruments that dominate the low end are kicks, toms, 808s, bass instruments, subs and the fundamental frequencies of the rhythm section. It is important to reduce the blend or crossover between low frequency instruments as it can create muddiness and a lack of power or fullness.
Here are some methods of processing bass!
1. EQ
Find the band of frequencies that dominate the bass sound and begin to scoop that band out of opposing tracks. In this case, a band around 100Hz is the most dominant sound.
This will essentially create room for the other sounds to reside and will also help with mixing when dealing with phase correlation.
2. Compression
If an instrument is too loud or becoming lost at times, compression will bring the audio to a more consistent level. Bass frequencies are best exercised as 'on/off', or in other words, present or absent.
Fluctuation or tremolo effects on the amplitude of low frequencies are rather difficult to perceive as intelligibility and articulation ranges reside solely in the upper end of the frequency spectrum. This is typically why producers will always apply compression as a standard practice rather than a reactive one, to level out dynamic range.
3. Multi-band Compression
A bass that uses a broad band of frequencies may benefit from the use of multi-band compression. Frequencies carry different characteristics depending on their location in the frequency spectrum.
As mentioned before, keeping sub bass information stable with a compressor creates a powerful low end allowing us to achieve dynamic range with the upper harmonics via softer compression.
4. Side-chain Compression
When a kick drum is triggered while a bass instrument is present, there is a brief period of time where the two low frequency instruments sum with one another as they are combined.
This summing can either spike the meters or destroy information...in any case, both are undesired effects for clean mixing.
Side-chain compression will compress the sustained instrument only when the kick drum is present. The instruments are now creating room for the other to hit.
The compressor will momentarily dampen the volume on a track depending on the side-chain signal and attack/release times set.
5. Arrangement
A great way to compensate for a large number of low frequency instruments is to offset them in the production stages. For example, when the heavy kick is present, allow it to pass before triggering the sub bass.
Arrange the sounds in such a way where there is little or no potential for low frequency instruments to clash. From a technical standpoint, this method is manually applying side-chain compression by physically chopping audio away where necessary.
Applying one or more of these methods will ensure your bass sounds powerful, full and controlled. As far as the sequence of operation, apply these effects in the order listed. Until you become comfortable with processing bass frequencies, then you may experiment with the order.