I know that the best servers are area 51, blackrock, illidan... etc. Just go through the list of the realms and set them by population and usually the ones that are highly populated are the best realms
Sylvanas
Laughing Skull is a pretty good Alliance PvP server as is Wildhammer on the US realms
The Horde is not better at pvp alliance is but horde are better at doing dungeons, raids and their much nicer then allis.
horde
VCN is Best PVP BG ARENA SERVER
Usually pvp realms do. a private server would have the lowest, due to the password protect on it
If you go in a arena team or in the gurubashi arena in stranholme vale (or somthing like that =P)
Yes you can, you send them just like regular mail, as long as it is the same realm.
it depends on the realm, some realms alliance-horde ratio 60/40 others it could bedifferent
There are Battlegrounds (more every expansion), and on PvP servers there is world PvP - more so now that Blizzard has implemented Cross-Realm Zones. PvP servers often have PvP oriented guilds that can help show you the places members of the enemy faction congregate. The recent Pandaria expansion is a good place to start if you are level 85+, the leveling zones in Pandaria a veritable hotbed of PvP.
In WOW (world ofwarcraft) there are different realms that you can select to play on. You can have a total of 10 players on each realm and a total of 50 characters across all realms. There are different types of realms too. There is a PVP realm (player vs player). There is a RP realm (role-play). There is a NORMAL realm (no special rules). There is a PVPRP realm (Player vs player / role-play).
There are many websites and resources that offer instructions on how to setup and install PVP software. The best website to get instructions on installation is the PVP website.