There are websites that you can print coupons off of. These typically are released at the beginning of the month and you will be able to print 2 of each. The three sites are http://www.coupons.com/, http://www.redplum.com/ and http://www.smartsource.com/.
Now you will also be able to print coupons off of some company's websites, these are typically "bricks" coupons. These means that when you click on the link for the coupon a new page will pop up and you will have to click the print here, when you do that it will go to your printer, however if you hit your back button a few times it will print the coupon again. This is completely legit, the bricks coupons are set to print two times and will not allow you to print more than two off of each computer.
If you have a grocery store that you have saver card you will want to check out http://www.cellfire.com/ and http://www.shortcuts.com/ and you will be able to add coupons to your saver card that will come off automatically when you scan your card. You can stack paper coupons with these to maximize your savings.
Now if you shop at Kroger you can go to http://www.kroger.com/ and do both print coupons and save coupons to your card.
These sites will help to start you off with getting your coupons plus help you to see what kind of coupons are out of there.