• reduce stress: simplify your life, take it easy
• sleep, rest, relax, meditate
• eat a healthy diet, with plenty of fluids, vitamins, yogurt, green tea, fish, fruits, vegetables (blueberries, broccoli), chicken soup, mushrooms (reichi, maitake, and shitake)
• exercise moderately (e.g., daily 30 minute walk)
• listen to your favorite tunes
• laugh, socialize, touch
• limit exposure to groups
• wash your hands; avoid touching your face
• avoid alcohol, sugar, red meat

Sources: metafilter, wellness, webmd