Mostly checking reviews and specs. My wife and I both use a StarTech dock at work and we have two at home. So far no issues with our Macs.

One thing to watch out for (when you are using a Mac) is to avoid Docks with a Realtek NIC. They use a generic USB driver on macOS that adds CPU load and usually only reaches 700-900MBit. Intel I210 NICs are great, they use PCIe over Thunderbolt and have a native driver.

I've tried several through work, so far Dell has been the only ones that just worked with everything. Lenovo was fine for most things, HP didn't even work with the laptop it was designed for.

I think the biggest thing is how much power the dock provides and how much attached devices need.