Best Theistic Arguments

[Neo-Scholastic]

I am going to debate a theist over the existence of god soon. What are the best arguments you ever heard from theists? Any tips on what topic to avoid in such an discussion? 
Thanks in advance

Their arguments normally consist of.
"without god how do you explain.." morals, matter, the universe, justice, laws of physics, beauty love or some other such thing.

And the atheist position is usually "it just is". It really boils down to the the Principle of Sufficient Reason. If you're going to debate a generic "theist" then you need sufficient reason to dismiss sufficient reason :-)

That said, a basic principle of debating is to fully understand the arguments of your opponent to the point of being able to defend them yourself. If you're asking the question then you probably are not prepared for a debate.

Making the positive case that 'god' -as if you or anyone else knew what this word refers to- does not exist, will just allow them to turn all your best points agains you.  Much better to stick to insisting that terms be defined and then challenge the legitimacy of the supernatural.  If not even one noncontroversial exemplar of anything supernatural can be produced, then that set can safely be assumed to be empty.

So basically, your advice is to play semantic games and argue over the meaning of words. That sounds more like sophistry than reasoned debate. It is the attempt to shift the debate away from the question of "that something is" to "what something is". It is a dishonest tactic. There is nothing of which anyone has complete knowledge. We are constantly learning and that is every bit true in theology as it is the natural sciences and mathematics.