The fader is a slider dial that controls the volume of a specific sound. This is an old-school technique that saves time and, if you're hiring a studio, money. This approach can afford you a very intense sound too. It relies on intuition and instinct and only very experienced engineers can do it consistently well. With a live band recording, you "ride the faders" as the band plays. This technique is distinct from typical approaches because it's rare to make fader adjustments in real time. For a more exact mix, producers typically set the levels before recording and make post-production adjustments.
One source of hot debate among producers and sound engineers is when to add effects. Some favor recording a sound as cleanly as possible, with no effects, so that they can exact more control over the tonal characteristics during post-production. Others favor applying effects before recording and doing very little post-production work. For example, you may elect to route the vocal microphone through a compressor unit before recording. The former allows for greater tonal control while the latter lets you create a live-sounding tone. One disadvantage of adding effects at source is that you can't remove them if you decide you don't like them.
Bus mixing is the practice of sending multiple tracks to a stereo bus. A bus is an area on a mixing desk where the sound of separate channels are grouped together and treated as one sound. Once routed to the stereo bus, the multiple tracks are rendered as a single track. While this prevents you from treating each individual piece of audio individually, it does speed up the mixing process. Sometimes it's beneficial to mix quickly before ear-fatigue sets in. Bus mixing is particularly useful if you are working with multiple versions of a similar sound, such as a collection of backing vocals.
This is the most typical approach to post-production mixing. Start with the lowest instruments and work up through the registers until you get to the vocals. Setting the bass end of the mix how you like it sets a tonal foundation. Start with the drums, then bass guitar, rhythm guitar, and keyboards if applicable, and finish with vocals.