Most polyps are not dangerous but over time some types of polyps can turn into cancer. So, to be on very safer side doctors remove polyp and test them and the doctor may want you to get tested regularly in the future.
You can prevent polyp in future up to greater extent by taking some steps:
Include lot of fruits and vegetables in your diet.
Eat less fatty food. Don't smoke and avoid alcohol.
Do regular exercise.
Loose weight if you are over weight.