Look up "nasal irrigation." The basic idea is to clean your sinuses with salt water using either a neti pot or a large syringe. There are youtube videos if you want demonstrations on how to do it. For people who suffer from persistant allergies and nasal infections nasal irrigation can literally change your life (for the better natch).
if there is an issue with congestion simply push your tongue against the roof of your mouth and massage between your eyes at the (begining) of your nose. its said to loosen the nasal cavity.
Mucines or sudafed, humidifier, eat something spicy like hot buffalo chicken wings, it always clears my sinus right up!
take a sinus medication before you get a sinus headache. I take mucinex.
mucinex*