You probably already own a modeling light
One of the more annoying problems of using little flashes for commercial, advertising or fashion photography is that they don’t have any modeling lights, so you can’t see the effect of the light until it fires. It’s not impossible to get around, of course. It just takes more trial-and-error to get your lighting right without them.
Well, I just had a head-slapper moment, when I realized that I have a modeling light for my strobes already. It’s small, lightweight and it’s already in my lighting kit. It’s called a flashlight, folks. I bought one shortly after I saw them on strobist.
If you didn’t get one of those, odds are you have another one. Dig around in your junk drawer. Pull it out and make sure it works. Set up a light stand with an umbrella or softbox already mounted and shine your flashlight into it the same way your flash would fire. Observe, adjust, move on. When everything’s ready, mount your flashes, and you’re ready to rock. This should take a lot of the guesswork and chimping out of your lighting decision making.
Enjoy and keep snapping!