I good idea when mixing vocals in a live setting is to set the vocal levels first, then bring the levels of instuments up behind the vocals, or lower in volume levels than the vocal volume level, but keeping in mind you want an overall balanced mix where every instrument (including vocals) have their own space in the mix.
That way, your instrument levels are not overpowering the vocals, and you are not trying to leave a hole in the soundstage to try to fill with the vocals.
Its always a good idea to have your reverb on the vocals matching the reverb on the snare drum, as these should be in the same space, without overdoing it.
Set the reverb on the vocals first, then match this on the snare.
By setting your vocal levels first then your instrument levels, the overall mixed sound should sound much better than having a vocalist trying to get over the top of loud instruments. Think of your favorite track and use this as a reference guide. The vocals should always be clear and have their own space.
Using your channel strip (highs / mids/ lows) really depends on the sound of your vocalist and using your ears in regards to how you want the vocals to sound. A good rule of thumb is using more mids / lows tends to give you a more fuller, rounded sound, but again, this is to taste. Using compression allows for the lower sounds to increase and the louder sounds to be clipped, which can equal out the vocals overall which helps when competing with instruments of similar frequencies, say like amplified guitars. Ratio / Threshold / Release etc on your compressor can be adjusted to suit, also makeup if the compressor has one (this makes up for the loss in db due to compression without increasing overall db), but a good starting point is a 2:1 or 3:1 ratio, release times can depend on the time between spoken vocals, so this can be set to suit. You don't want too short, or for that matter, too long a release time, but find a happy medium that suits your vocal/ song timing.
Remember, practice makes perfect so the more you play around setting your levels the better at it you become.