Decide what you want to see on your watch during normal operation. For example, I want to see my heart rate and the time. Some people want to see calories burned, time elapsed, etc. Make sure your watch gives you the combination you want without having to switch back & forth.

If you're spinning indoors, sometimes the lights are low. You might want a monitor that lights up.

Make sure that it doesn't get interference from other monitors, telephone poles, etc. All of my Polars did that. Annoying. (I have a Sigma now & I love it.)

Make sure your chest strap is snug. If it is cold & I'm not sweating, I use a electrode gel to get a good connection. I have a small chest & I had to cut the elastic & make it smaller.

When I started cycling, I had a cadence monitor & loved it. Now, I don't & find that I really don't miss it much. You get used to what feels right for your body. Just don't mash big gears or over spin so that your knees hurt.