Simply trying to remember your dreams proactively (i.e. planning on remembering them before you go to sleep, thinking about them constantly, etc.) has a positive effect - and the dream journal contributes to this. Waking up soon after your REM cycle (the ~30 minute period where you dream) means dreams will be fresh in your mind. This can be quite hard to accurately plan, but bear in mind each set of dream cycles (light sleep, deep sleep, dream sleep) tends to be roughly 90 minutes long, so plan to sleep for 6, 7 1/2, 9 hours, etc.

Additionally, do you drink or smoke? These often reduce my recall to virtually nothing the night after.