The only thing you need to do is enable the htaccess (should be there by default) then set the URL Structure option in Admin>General to the top one. If you have problems getting it to work checkout the dozens of questions about it on this site.
Everything else you need is included such as good titles, headings and meta description, generally good clean HTML. Plus Q2A is pretty fast in most cases (except if a question has 100+ answers, but that will be fixed soon).
