The more you know! Apparently, you should not rinse your mouth with water after brushing your teeth. Instead you should spit, in order to keep the fluoride from the tooth paste on your teeth as long as possible. Here is an article about it by the Oral Health Foundation: Spit, don’t rinse.
If you’re really ready to go down the rabbit hole of internet dental hygiene, here is an article stressing the importance of flossing.