Well I think it is important to realize that all faith is a bit irrational. By recognizing this you'll avoid looking like an idiot when arguing with atheists. If you argue from nonsense you'll reinforce their preconceived idea that your faith is totally irrational - which it is not if one considers the external (extra-biblical) evidence that supports it.
Saying the 'Bible is true because it says it's true' is idiotic. Saying "Look at all these things the Bible says & how they are supported by archaeological records, external writings, etc..." makes one's argument a whole lot more sensible.