As we know, the default admin URL for magento is /admin, Using this url for your live site is not safe as anyone who has expereience in magento can easily guess this url and try to hack your admin area. If you are not really luck, you will be screwed up. To change the existing admin router to something new, Step 1: go to your app/etc/local.xml, which will have the content as below

    
        
            
        
        
            
        
        false
        
            
                
            
            
                
                    
                    
                    
                    
                    
                    
                    
                    
                    1
                
            
        
        
    
    
        
            
                
                    
                
            
        
    

Step 2: Change
    
to
    
Step 3: Ftp to your site, clear var/cache directory.
You are all done! Access your site admin with the tough to guess URL ;)