1.) Sign up for a free email account with gmail, yahoo, or whatever. Use that email address when filling out forms, and don't worry about checking it. Or check it rarely. Whatever floats your boat. You can sometimes get other good offers from filling out the forms, so you may want to check it on a regular basis. At least it won't be getting mixed up with your regular mail.
2.) This is a wonderful tool. www.mailinator.com You don't even need to go to the website to make use of it. When filling in the email address, just make something up. email@example.com. firstname.lastname@example.org. email@example.com. It truly doesn't matter. Anything you use with the mailinator address will be caught on the mailinator server. You can go out and check it if you want. It's public, anyone can check whatever address you use. But anything that goes to the address is only out there for a limited time, then it gets deleted. Automatically. You don't even have to see it. So neener to the spammers!