"rate" - This setting controls packets to ensure a good connection. If you have an ISDN modem ( 128K ) then this can be set to around 12000. If you have a 56K modem then this should be around 4000-5500 depending on your connection speed. If you are on a LAN or have a ADSL modem ( lucky bastard ) then this can be around 25000 or perhaps even higher. Remember, it is best to experiment to find a suitable number but don't get too carried away or you may cap performance. "snaps" - This is possibly the most important setting for getting a good connection. As everyone knows, in Quake 2, your gameworld updates depended on your current FPS so slower computers were at a disadvantage. Now, in Quake 3, your snaps setting determines how many updates you recieve from the server. 56K modems should have a setting of around 20 - 30. ISDN modems (128K) should be around 40 as should any other fast connection devices ( LAN, T1 etc.... ). Remember to read my cg_lagometer section for tips on "snaps".
"cl_maxPackets" - This setting puts a limit on the maximum amount of packets that can be sent to the server via the client. This setting is useful for people with slower modems. The default setting is 30 ( comparable to a 56K modem), but lower this if you have a 33.6K modem or less, and higher this setting if you have an ISDN or higher modem.
"com_maxFPS" - This command limits your maximum FPS. You may ask why you would want to do this, and the answer is that it will help the server from having lag confusion when your frame rate has a sudden rise or fall. Run a timedemo, collect your average FPS and use that as the limit for when you play on-line. While you are playing off line, keep this setting at its default ( 85 ).