A question about .htaccess

You can just add the .htaccess to the root of the website however be cautious as WordPress will have added it’s own if you have changed the link slug structure within the WordPress admin.

In the htaccess file you should use 301 re-direction’s like so:

redirect 301 /oldpage.asp http://www.thesite.com/newpage/

If it is a big site then you will not want to re-direct all pages although it could be worth while. I normally just do a Google site: search and re-direct the most important pages and any with first or second page listings.