One of my first mistakes as a couponer was signing up for each and everything I could find with my personal e-mail account. I use my e-mail to keep in touch with family,friends, for business purposes, etc. and overnight I had hundreds of unread messages because of my mistake! If you use your e-mail for actual emailing, it is a good idea to have a separate e-mail account specifically for your couponing!
Now that I have one of these, I do not mind signing up for newsletters just to get coupons or signing up for contests because the e-mails that come through don't clog up my inbox and all the coupons that come through e-mail are all in one place :)
There are so many sites that send out Spam e-mails nowadays so just be careful on what you sign up for. When you are viewing websites, make sure you signing up through a corporate website or the actual manufacturers website instead of every little random site that says they'll give you coupons :)