The main things are to set up you mplayer.ini file correctly and to get up-to-date paints. The paints you can get from Flybert, http://www.flybert.net/ . The latest version of mplayer.ini, (with the right server addresses), you can pick up at Wings of Valor I am sure, http://www.wings-of-valor.net/ , while taking a look at the MMP docs in their documents section. Here is a version of mplayer.ini posted there by the fellow known here as Laser in April 2007:

;This file contains the names and/or IP addresses of known game
; servers. Any additions to this list will be checked for inclusion
; in the list of available servers. Note that each entry should be
; of the form 'Server=ip_address'.
[KnownServers]
Server=UDP:198.74.40.74:47807
Server=UDP:209.67.71.137:47807

[MetaServers]
//Server=TCP:rb2.west.won.net:6001
Server=TCP:rb2.east.won.net:6001
Server=UDP:dyn-meta.dynamix.com:47801

[QuickChat]
Insert=This is an example of my first chat macro
Delete=Follow me boys!
Home=Let's go bomb something!
End=Nice shooting!
PageUp=Salute!
PageDown=Hey! Watch the hair, pal!

;Use the following entry if you are playing behind a firewall, and you
;need to specify a particular port number to access the internet. In
;most cases you should leave this blank...
[Winsock]
Port=


Also, you must be sure that you are using a "stock" version of the game.

As ever,
Birdbrain