Snapshot errors cannot be avoided as we would have to limit the amount of props in the server, which would be too low for everyone. A "Snapshot Error" means that there is too many props in the server to send you the locations of them all. When you join the server, before your able to see anything, the server sends your client a list of what prop is where and everything else. Where there are lot of props, this list gets huge, and when the server tries to send you all the locations, your client gets overflowed by how many props there are, thus giving you this error.
I'm noticing a problem. No matter how I try and connect, I get an error: "Server uses different class tables.".
Grab the copy of gmod9 from the forums here in the downloads thread and then do this: Change the appid in your gameinfo.txt file from 220 to 215 by going to your gmod9 folder (usually C:\Program Files\Steam\steamapps\SourceMods\gmod9 or C:\Program Files\Valve\Steam\steamapps\SourceMods\gmod9.) and opening the file gameinfo.txt. Find where it says "SteamAppId 220" and change 220 to 215, so it should now read "SteamAppId 215". Save the file and restart Steam.