Hey gang! I'd like to share a little insight with you. When I was in elementary school, one of my teachers told us that life was about solving problems. It took many years, full of trials and tribulations for me to realize how true her statement was.
So how does this relate to music? As a musician we are faced with many issues. One of the disfavor-able issues with playing live is either not being able to hear yourself well or not being able to hear yourself the way you’re used to. I have yet to be in a situation where I could not hear my bass at all, but there's always a first for everything lol! I've learned that being proactive with your stage amp can go a long ways.
First off, if you’re using the DI built into the amp, it will usually have a way to select whether you want the DI to be pre or post eq. Since my signal is always going to the house (PA system mains) and monitors, my amp serves as my own personal monitor. You want to have the DI set to "pre" as this will allow your signal to be taken before the eq section, allowing you to make adjustments to your amp without affecting the FOH (front of house) and/or monitors. If the soundman plugs your bass into a DI box then runs a cable out and into your amp input, you will be in "pre" mode, as your signal is taken before the input of your amp.
Second, if your amp is not positioned properly you won’t be able to hear an accurate reproduction of your bass, which could cause potential problems. A gig saver for me has been a sturdy, foldable, and lightweight stand I purchased from Home Depot. This allows me to prop the 2x10 or 4x10 cab around 30" off the floor. At that height I can totally hear everything much better as opposed to on the floor where the sound is just blowing past your legs. It's incredibly useful when having to stand very close to your amp. It also isolates the cabinet from the floor which is a good thing if playing on a wooden stage which can sometimes act like a giant subwoofer and send vibrations up through the mic stands potentially causing feedback. If I’m in a really cramped situation with a combo amp, I'll try to "monitor style" the amp. As long as you have something sturdy to support the amp from falling back, you can tilt the amp back to your desired angle.
It's also a good idea to run these ideas over with your soundman first to make sure everything's cool. He or she will eventually be thankful for this as it makes their job easier.
It's all about being proactive!