I've actually got a few pieces of advice.
1. It's not something that you can do every once in a while, You need to practice... A LOT!
2. If you use a smaller rig with a smaller camera, It's easier on your body, but harder to keep the camera stable; If you use a bigger rig with a bigger camera, it's harder on your body, but easier to keep the camera stable
3. If the director ever says something along the lines of, " We don't need to put the camera on a tripod for this next shot, you can just hold the camera still on your Steadicam!" Hit him/her over the head with the largest object posible Politely sugest that they put the camera on a tripod, the shot will turn out a lot better. (and then give them a "You must be crazy if you think I'm doing that" look)
4. Avoid bumping into things, people, and large aquatic mammals (small aquatic mammals such as dolphins and platypus are okay)
5. You will spend almost as much as the rig on accessories. It's somehow become agreed upon that Steadicam ops need to supply things like Bartechs (sometimes you need 2-3 for things like iris and zoom), power cables for every camera ever made, wireless video transmitters, batteries, vehicle mounts, more batteries, etc.
6. Have fun doing it. If you don't end the day exhausted, but with a smile on your face, you did something wrong.