In addition to not blowing your nose too hard, don't hold in a sneeze, and don't fully occlude one nostril when blowing your nose (sometimes when you have a cold, this is so effective that you can't not do it... just don't do it too often).

Colored snot alone is not indicative of a sinus infection - this can result from a cold virus, or even allergies. Excruciating and/or long-lasting facial pain is generally the hallmark. If it lasts longer than two weeks, go see a doctor.

Having been a long-time sufferer of this condition, I can recommend a particular neti mix. The usual is straight saline (1/4 tsp salt to 8 oz water). I've found that with the addition of xylitol (1 to 1.5 tsp to 1/4 tsp salt), tea tree oil (2 drops to 1/4 tsp salt), and providone-iodine (0.5 cc or ~15 drops to 1/4 tsp salt), I can actually knock my chronic sinus infection into remission for some number of days or weeks (basically until the next time something irritates my nose and the bacteria throw a party again).