Merging a client's 10 websites into 1 - redirect? rewrite?

I have a client who has a bunch of sites each with content, articles, page rank and many visitors... I recommended them to reorganize into ONE MAIN SITE.

What's the best way to have all the old sites redirect to the new one IN ORDER TO not lose traffic AND pass pagerank onto the new main site?

DNS redirect?
a htaccess file in public html of each old site?
....

 

I would go the htaccess route, myself. Make sure to keep track of 404s, and use a 301.