don't over think it, the key is to relax. no one can turn their mind off and sit quietly for hours their first time. start slow and move on. find a comfortable quiet area, close your eyes, and take ten slow deep breathes. if you have time, do ten more, and slowly work your way to fifty. over time you will work your way up to a minute, then five, and so on.
also there are various forms of meditation, so find the one thats best for you. remember, just relax, you don't have to clear your mind, let the thoughts flow, don't dwell, so long as you feel relaxed, you're doing fine.