Having done a few sites in Joomla now, i'd have to say don't worry about any seo plugins too much.
The only plugins I have is xmap (for my sitemap) and another one which allows me to give section and category metadata which Joomla fails on somewhat.
Other than this I make sure I have sef urls turned on (under global configurations), then if you want to do anything else, look up .htaccess in google. This is a file where you can do lots of url re-writting and more!
In this file I:
1) Create clean urls for my affiliate links:
http://www.clearlycasino.com/visit/intercasino.html
Code:
redirect 301 /visit/inter-casino.html http://www.intercasino.co.uk
2) Gzip files for faster load times and smaller file size:
Code:
<ifmodule mod_deflate.c>
AddOutputFilterByType DEFLATE text/text text/html text/plain text/xml text/css application/x-javascript application/javascript
</ifmodule>
3) Add some file caching
Code:
<FilesMatch "\.(ico|pdf|flv|jpg|jpeg|png|gif|js|css|swf)$">
Header set Cache-Control "max-age=290304000, public"
</FilesMatch>
4) Rewrite any other urls I see fit
5) Ensure there is not two versions of my homepage (e.g clearlycasino.com and clearlycasino.index.php
6) A few other things as well