Robots.txt Generator Tools will create an robots.txt for your website. robots.txt is very useful to control bot when they visits your website, weather you allow bot to access your web or not. and decide which folder you do not allow bot to crawl, e.g folder for administrator.
To control robots that come to your website simply generate an robots.txt text file with above tools then place it at the root of your domain. For example, if your domain is http://www.yourdomain.com, place the file at http://www.yourdomain.com/robots.txt.