If you join a server and it turns out the average lag is higher than it said on the server list, and you know you won't be coming back:
Drop the stuff you've collected somewhere. Near a camp if you know where it is, near the gate if you don't. (This one mostly counts if it's in the first few days, but it depends on what you've found.)
I know this is right in the first post, but it bears repeating. Nothing quite like seeing people join once and never show up again, and having an entire biome or two be almost completely bare because people didn't drop what they picked up.