To make a 301 redirect for a changed page, you need to add the following into a .htaccess file:

redirect 301 /old page name your.domain.com/new page name

So for example, if you wanted to redirect www.oldsite.com/smith.html to www.oldsite.com/jones.html, you would put

redirect 301 /smith.html http://www.oldsite.com/jones.html

To prevent google being confused about your site (Is it http://yourdomain.com or http://www.your.domain.com

Just add the following to a .htaccess file

RewriteEngine On

RewriteCond %{HTTP_HOST} ^mywebsite.co.uk
RewriteRule (.*) http://www.mywebsite.co.uk/$1 [R=301,L]

This will cause anyone who uses mywebsite.co.uk to be automatically redirected to www.mywebsite.co.uk