How about we start with tiering. Before even making a team, you must know how tiering works.
Ãœber; This is the tier that holds the strongest Pokemon, everything is fair play here, and Pokemon get into it by being banned.
Ou (over used); This is the tier most people use. Every Pokemon that is not Ãœber is allowed here, Pokemon get the Ou status by how often they are used in their tier.
Bl; This is another ban list, Pokemon that are deemed to powerful for uu get placed here. These Pokemon are often Ou worthy, just don't get enough usage.
Uu (under used); These Pokes often times were Ou at one point, but have lost some favoritism. Any Pokemon that is not in the bl tier or above is usable here.
Bl2; This is the last ban list. Pokes deemed to powerful for Ru get placed here.
Ru (rarely used); I don't know much about this tier. Basically anything that's nu and ru can be used.
Nu (never used); This tier is for the weakest of the weak (ignoring pu, I don't count that though). This also happens to be the largest tier with the most creativity.
Here is a link to the tiers;
http://www.smogon.com/bw/tiers/
Any questions about tiers?