Daily Surveys can be taken one or more times per day. This is indicated in the survey description. Other targeted surveys can be taken as you see them. Be sure to complete these when you see them. Some surveys may accept a limited number of responses from people matching your demographics, and can sometimes disappear quickly. New surveys come out all the time too!
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.