If you're looking to make some extra cash in your free time, paid survey sites can be a great option. To earn the most money on these sites, it's important to sign up for multiple sites to increase your chances of receiving survey invitations. You'll want to keep your profile updated and provide accurate information to increase your chances of being selected for surveys. Additionally, be sure to check your email frequently and respond promptly to survey invitations. Finally, be patient and don't give up if you don't qualify for every survey – keep trying and you'll eventually earn some extra money.