It is not as easy as you think. Check the post above about “EQ hints”. Understanding how EQ works and what each frequency sounds like is key here. If the bass is sounding really muddy and really taking over the mix look to reduce the 200-400hz area. If your low end seems to be getting slammed by the PA system or the guitarists, reduce the 150hz and lower areas. Subwoofers at shows typically crossover around 150hz – reducing your rig’s sound here will allow you to hear the low end from the PA while hearing your on stage rig simultaneously. If the band just seems scary loud in the midrange, a small cut at 600hz will help you hear yourself better. Keep in mind that lowering the low end content on your bass will allow you to hear every other frequency better than before. I suggest removing certain frequencies until you start hear your bass tone better. Then boost an area or two and see what happens. Small cuts and boosts will help you the most.
Lastly, check your amp and make sure you are not using any of those “Shape, Enhance, Ultra Low, Contour” style buttons. These buttons or knobs basically reduce the midrange and up the lows and highs. They SUCK for a live situation in ALMOST every case. Good luck and message me for anything else!