Changing admin path name is one of the important steps to secure your magento store.There is an option to change default admin path during installation.But you can also rename admin path after installation.
To rename admin path,
Goto to /app/etc and open local.xml file.
Find the text ![CDATA[admin]] in the file(around line no.57).This is the default admin path.
Change admin name to some other name like mystore and save it.
So it will look like ![CDATA[mystore]] and admin url will be