1. Replace your toothbrush every 3-4 months: That is what the American Dental Association recommends. However, if your bristles are frayed or you get any respiratory or oral infection, replace it before then. And if you have a weakened immune system, replace your toothbrush more often -- including if you're recovering from illness or an experience (like surgery, childbirth or breastfeeding) that lowers your immunity.
2. Rinse your toothbrush before brushing: Doing it after brushing might be automatic for most (nobody wants old toothpaste foam on their brush). Rinsing it before will also take off anything extra that got on it while you were away. It also helps soften the bristles a little as toothpaste deposits may have hardened them.