When starting genealogy, you should ask yourself what you want to accomplish with your research.
Are you primarily curious about your ancestors and want to see what information is easily available? Do you want to devote your life to uncovering and preserving the past?
What parts of your family do you wish to research? Some people prefer to focus on a few lines and mostly ignore the lines that marry in. Some people collect every person that can be tied in, including every umpteenth cousin many times removed. What about adoptions? Which line do you research? If you have a surname to research that isn't very common, will you research anyone with that name, whether there is any known connection to you or not ("one-name study")?
As time goes on, your scope may change. But try to determine at the beginning what you wish to research in order to avoid re-doing previous work.