How to balance kick and bass
Place a finger on the woofer to feel bass and kick relationship. Make sure the one and the other are not messing up the groove. Fix bad grooves with balance, HPFs,1 and even phase correction plugins (see Put your bass and kick in phase). You can also try Sidechaining kick and bass.
Mixing the kick below the bass can work well for slow music that needs kick impact. Mixing the kick above the bass is better for fast music, since sub frequencies are slow, taking longer to complete a cycle. Pop and hip-hop generally mix the kick above the bass.2 Check what are the fundamentals of the kick and bass before making a decision too. Sara Carter likes to leave 30Hz for the kick.3
Warren Huart often cuts ~110Hz on the kick to make room for bass.4 Elsewhere, he has said it may be between 80-100Hz.
Jacquire King solos the kick and gets it hitting -3VU. Then he adds the bass and sets it at a level where the bass and kick together hit 0dB VU.5 Sara Carter does something similar, hitting her master at -14VU and mixing kick to -7 or -5VU, then adding bass so it hits -4 or -3VU.6 The rule here seems to be having the bass add 3VU of gain after the kick.