Ah, dream recall. What an illusive and yet such an important aspect.
It is, in fact, the first thing most train when starting on the road to lucid dreaming (when following certain guides and the such).

Search over the forums and I'm sure you'll find many topics on the idea of dream recall improvement, which should help.

My advice would be to keep a firm intent on remembering dreams if you do not wish to disrupt your sleep. If that is not a problem for you then waking up in between REM periods (periods of rapid sleep, when dreams occur) is a sure-fire way to remember dreams. An excerpt from LaBerge's "Exploring the World of Lucid Dreaming":

(1) The length of the REM periods increase as the night proceeds and
(2) The intervals between REM periods decrease with time of night, from ninety minutes at the beginning of the night to perhaps only twenty to thirty minutes eight hours later.[/b]