Over time you're probably not going to stick with just the sites I recommend. And that's a good thing. You should check out new sites and register for multiple ones. But this also means that there's a greater chance that you'll fall prey to a scam. I'm here to make sure that this doesn't happen.
1.) I've said it many times but it's vital: a legit site will not ask you for money! Sometimes there are charges if you want to update your account, and this is okay although I don't recommend it. You should be perfectly fine with a regular account. But never trust a site that has a sign-up fee!
Note: This includes sites claiming to have an exclusive list of legit programs. Do not pay to sign up for them. There are plenty of free ones so you really have no need to anyway.
2.) Use your logic when viewing new sites. Legitimate companies have professional designs, little to no grammatical errors, and a lot of information. You should always try to search around the site, making sure there are no broken links, etc.
4.) Do some research. Google the site. Look through reviews, message boards, etc. to see what others have to say about the site. This will usually be a primary indicator of whether it is legit or not because when you have enough sources, they can't all be working for the company.
5.) Check out sites that expose scams and search for the company. They usually include all kinds of customer complaints, too. Check out the section on scams at Snopes.
6.) If you're ever really unsure, just walk away. Even if you would not be losing any money, it's not really worth it to lose your valuable time.
As always, Happy Money-Making,