Mime is one of my favorite improv tricks. I guess it's not really a trick, but it is one of my favorite things to do. Here are some of the mime related things I've learned over the years:
"This is not a gun"
The Have Nots gave some great mime advice in one of our first workshops with them. One of our scenes featured someone with a gun, but they were doing the whole my-index-finger-is-the-barrel-of-the-gun thing. That motion works for children, but we're improviser we can do a little better. Mime guns as if you're holding an actual gun. Mime phones as if you're holding an actual cell phone. Again this will help ground your scenework in reality.
Not only do we make our hands into the object rather than pretend to hold an object, sometimes we pull out an actual object. Typically, wallets or keys or whatever an we may have literally brought on stage with us. If someone is miming a gun (in the proper way of course) if the character they're mugging brings out a real wallet, it just draws attention to the fact that the gun isn't real. Similarly, when undressing, don't actually take off clothes. It's just weird.
Slow it down
Improvisers tend be very dialogue oriented, always trying to think of the next funny thing to say. Thus, when we mime things the actions occur very quickly. Chopping down a tree in improv only takes a few swipes. Driving to the store only takes 20 seconds. Undressing occurs in one motion.Mime imperfect objects
I recommend that we should take our time with mimed activities. For one reason, it will help ground our scenework in reality, but mime is also fun to explore. Details are a comedy gold mine. Just like saying "look at that thing" isn't as fun as saying "look at that slow lauris," being specific with your actions is more interesting than generic movements.
One interesting thing you can explore when you mime objects is imperfect objects. Just like cartoon characters, we can pull whatever object we need out of the air, but consider exploring imperfect objects. I've seen improvisers that were miming getting dressed grab belts that were too small for them. The audience loves to see characters struggle. Objects that don't do what they're supposed to is a bit you can play with in scenes and get a lot of mileage out of it.
There are dozens of things you can do with mime. Slow it down and give it a shot!