ahh, the levels thing - my mixer has got individual VU metres for each channel then another for the main output - which are independant of each other, by that i mean you dont have to press a button on the VU guide thing to change from the main output and cueing input/output...
that vestax 3 channel (exact name escapes me, but it's one the most popular vestix ones..) doesnt even have the ability to see the level of what your cueing.. so you have to do it blind, 90% of the time it will be too loud or too soft...
so when using mine, the VU metres for each channel is there, infront of you (no remebering to press switches, change the VU display etc..) and the one your playing is next to it, you can match em up exactly....
levels r the most important thing (after beat matching i spose) when mixing imo....
esp if your sound system is running right on that edge (which most of the time it does, cos it sounds wicked at that point)
one bad level can blow the whole thing (if you dont have a limiter/compressor) and coming in too quietly is just as bad, cos the sound technician might turn up the mixing desk
(mixer->mixing desk->sound processor->amps->speakers)
thus when you next put the levels back to 0, you could cause it to blow (as the signal into the mixing desk goes up, which has already been turned up, cos youre level was to low...)
make sense?