Very miniature post.
When arguing with theologians, apologists philosophers, bible thumpin' preachers, new age hippies or anyone else who likes to claim they can 'prove' the existence of this or that magical thing, keep in mind that you must agree on the premises to start. I always make sure the premises are very, very clear and spelled out. I never let my opponent start his argument until these basics are settled.
Some wonderful examples come from Christian apologetics. All of Aquinas's 'Five Ways' start with premises I and any materialist, humanist, rationalist or empirical rationalist would instantly disagree with, making anything that follows pointless. They all begin with the basic premise that you must have a first of everything, but somehow that first can be exempt and must therefore be a thinking being called God. This is both the premise and the conclusion, and if we shut down the premise we don't have to deal with the painful tautological and circular shouting logic.
Another favorite is of course the ontological argument, in it's myriad forms. It depends entirely on no one paying attention to the premise. It quietly offers a (very fuzzy) definition of perfection, then tacking on the idea that existence is in itself a quality of something and fails to even mention these two points. Many long and quite eloquent deconstructions and defenses of the ontological argument exist, but they can be entirely avoided if we simply refuse to allow the poorly thought out and fanciful premises.
None of this means you can just be disagreeable or ignore reasonable premises, but it is a good way to kill many arguments. The premises must be agreeable, they must make sense from either earlier arguments, evidence, or they must be self evident in the simplest way. Otherwise no amount of argument will decide anything.
For those of you trying to prove some god or another, don't whip out arguments without stating your premises clearly. If you try to gloss over them you can't win, you can only bully.