im new to all this and I was reading how redesigning a website can hurt your google ranking if you dont redirect the old links. My main page has the same domain but the 3 or 4 sub pages have different names, how do i tell google to redirect the old to the new?
You'd write the 301 redirect into the .htaccess file on your server. If you're using a CMS like wordpress there is an easy to use plugin that does it for you. A good way to find out which pages should be redirected is to check Google WMT or to do a site: search for your URL and see what's been indexed in google and which of those pages are now 404ing. Hope that helps
If you will redesign your website then you should mind website url. Copy old url and redirect at new url by using 301 redirect (.htaccess file). Thanks
Best option is to preserve old names when creating new website. But if you cant keep old names, you can use 301 redirect in htaccess to redirect pages to new pages. You can easily find these issues in Google webmaster tools.