Factors which may predispose you to developing sinusitis include: allergies; structural problems such as a deviated nasal septum; smoking; nasal polyps; carrying the cystic fibrosis gene (research is still tentative). A recent advance in the treatment of sinusitis is a type of surgery called FESS - Functional endoscopic sinus surgery, whereby normal clearance from the sinuses is restored by removing the anatomical and pathological variations that predispose to sinusitis.
Self-help measures include simple painkillers (aspirin, acetaminophen or similar), inhaling steam, hot drinks including tea and chicken soup, over-the-counter decongestants, and getting plenty of rest. If sinusitis doesn't improve within 48 hours, or is causing significant pain, one should see a doctor, who may prescribe antibiotics or nasal steroids.
For chronic or recurring sinusitis, you should be referred to an otolaryngologist for more specialist assessment and treatment, which may include nasal surgery.