1. If you do not want to have your personal e-mail box filled up with coupons, offers, surveys, etc. create a separate e-mail address for just that. Some people even take it a step further and create one for surveys and one for offers/coupons.
2. If you don't want to get phone calls at home from offers you signed up for, sign up for Google Voice. It's FREE and will create a new phone number for you. You can give this number out when you sign up for offers and Google Voice will take messages for you online. There is more info on Google Voice here.
3. If an offer is FREE for a certain amount of time make sure to put it on your calendar before the trial is up so you can decide if you want to keep the offer or not so you won't be charged if you don't want to be.