One thing that Final Fantasy XIV: A Realm Reborn has to contend with that other MMORPGs don't is the fact that there are essentially two player types. You have the people who played the original game, and the people who will be trying out FFXIV for the first time. What makes these two groups so different is that the classic players, referred to as legacy players (not to be confused with Legacy status), get to import their characters, progression, equipment and gil (in-game currency) to the new game. To help level the playing field, legacy players can only import 10 percent of their gil, but all NPC-sold items are also reduced to 10 percent to equalize the in-game economy.
While legacy players have the option to start over with a new player, Square Enix created a few restrictions to level the playing field. To allow new players to catch up and not jump into a game with a preset economy, there are legacy servers and normal (non-legacy) servers. Any legacy player wishing to use their existing character, is restricted to playing on legacy servers. A new player can start on a legacy server, and a legacy player can create a new character on a normal server, but a legacy character cannot be played on a non-legacy server.
The legacy servers in the US are Balmung, Excalibur, Hyperion and Sargatanas. The European legacy server has been designated as Ragnarok, and the Japanese legacy servers are Aegis, Durandal, Gungnir, Masamune and Ridill. Every other server is a non-legacy server. In addition, while you can play on any server from any region, the regional designation represents the lowest ping to the server. So if you're playing from the US, but want a lot of Japanese players to party with, you can still play on a Japanese server, but you may experience a bit more latency.
Now that you've decided if you want to be on a legacy or non-legacy server, and which region you'll be choosing, it's time to get to the important stuff. Where will some of the more popular online communities be playing? Now you may be thinking, "Why would I care where various online communities are playing?" Have you ever played an MMORPG on a server that was overrun with people role playing? They embody the character races and speak (type) as though they were that race. It's a fun and entertaining experience for some, but it may not be for everyone. The role-playing community has chosen Balmung (legacy) and Gilgamesh (non-legacy) as their unofficial serves in FFXIV.
In addition, Giglamesh is the Reddit server of choice. If you'd like to be able to adventure with your fellow Redditors, Giglamesh is the place to be. You can discuss your adventures on the FFXIV sub-reddit and have an offline experience when you're not playing. The same can be said for one of the largest online gaming forums, NeoGAF. The community there will be playing on Sargatanas (legacy) and Ultros (non-legacy). NeoGAF players are generally very helpful, and many of the legacy players will be creating new characters on Ultros, so they'll have plenty of experience to fall back on.
When it comes down to it, the server you pick in an MMO won't have a huge impact on your enjoyment of the game. If you want the least amount of latency, select a server in your region. If you don't want to deal with an existing economy, don't pick a legacy server. If you aren't sure you can handle hearing people role-play, don't pick one of the role-playing servers. If you're not a fan of Reddit, avoid the Reddit server of choice. With those decisions out of the way, there isn't much more to concern yourself with in regards to server choice.
If you end up not enjoying the server you're on, or you have friends on another server, after roughly six months Square Enix is allowing people to change servers. There will be a small fee involved, and if a server is overcrowded you may not be able to transfer there, but otherwise all transfers will be approved. After six months, the pre-existing economies of legacy servers shouldn't be all that different from the non-legacy servers, so you won't have much to worry about. Keep an eye on Prima Games for more Final Fantasy XIV: A Realm Reborn tips and strategies in the coming weeks.