1. Your 404 error page should be very attractive..
2. It should look like a part of your website..
3. It must contain links to all the important pages of your site..
4. It should have a search bar..
And personally, I don't think there is any need of redirection.
Make it a customized 404 error page that keeps you on your website rather than navigating out of the site.
Firstly, add a line to your .htaccess file like this:
ErrorDocument 404 /404error.html
Substitute your own 404 page’s URL for the ‘/404error.html’ bit. However, please remember not to use the full NAME e.g. http://www.yoursite.co.uk/404error.html here or this will send the request to the web and create a ’200 OK’ header response instead of the “404 NOT FOUND” response we want.