Following up on my previous post about having a choice in your army - I want to explore why you choose your army (or your second or third army).
Now, the following items can be done in any order and will weigh different for each person.
Assuming money is not an issue (which it probably is, this is not a cheap hobby! More on this later), you should consider how the army...
Consider how it plays. Do you like moving lots of models or being capable of out maneuvering the foe? Do you enjoy the feeling of throwing down huge amounts of dice at a time? If you're a new player, you might have some issues finding out what army strengths you favor. In my experiences, your FLGS (Friendly Local Game Store) will have several armies that you can play with in order to learn or if you want to try out a different army. Pay them a visit and see what they have in store.
Everyone has their own aesthetic taste. Needless to say, this will affect some people's decision more than others. Do you like how a certain army looks over another? Is it the models themselves that you enjoy or the GW-eye candy color scheme? Look at lots and lots of miniatures from different armies and different painters and see what catches your fancy. Now, a lot of people may give me some flak for this but I recommend buying a blister from two or three armies if you can't make a decision. Usually, a blister pack is pretty representative of what you can expect for the rest of the army. I know before I started Eldar and Salamanders, I spent a huge amount of time going through the Coolminiornot.com galleries looking for anything that was just gloriously inspiring.
Are you always the good guy when you play video games? Do you just hate the idea of people acting perfectly in line? The fluff behind each army is probably an indicator to whether or not you'd enjoy it. So far, I haven't met a single goodie-two shoes who would enjoy purging plastic life from the tabletop while screaming "BLOOD FOR THE BLOOD GOD!" It could happen, though.
Now, I'd like to know why each of you chose your specific army? What attracted you to the cry of Khorne or the Path of the Seer or to heed the Wolfcall?