My looks like this:
set realmlist logon.monster-wow.com
set patchlist logon.monster-wow.com
set realmlistbn ""
set portal eu
You do not need to change "set patchlist" line, but I did it, so I can not update it any further by mistake. You can also add # in front of it, which will make it comment line and WoW will ignore these lines. Useful if you are trying multiple servers. With it you can just comment other "set realmlist" lines, and quickly switch between them.