Parallel processing is a technique for mixing an effected version of a track with a dry version. This is particularly helpful when you want to process a sound but the plug-in doesn’t have a dry/wet knob or you want to be able to control the effected signal with additional effects, such as EQ, reverb etc.
Spectral analysers are a useful tool for helping to diagnose troublesome frequencies in your mix, weather it be low-end rumble, a pokey mid-range spike or a piercing high frequency.
There are numerous sample packs offering club-ready kick drums and this is by no means a bad thing. However, these might not always be suitable for your track.