What exactly do I need to do to make sure and take advantage of each directory submission I make for my website? What should I be putting in the title, keywords, description, etc....
Don't be spammy. Have a short, descriptive title and a good description (not too short) that's in sentence form. Also, submit in the correct category. Be careful of deep linking (linking to files or folders on your website that is not the main index page), some directories allow it others don't. Look at the titles and descriptions in popular directories and go with something similar. The DMOZ would make for some good examples.
I would also use something like http://www.roboform.com/ Its free and makes your submissions so much easier.
Some sites don't allow keywords in the title, as they only accept the site name. Every decent directory has submission guidelines. As far as keywords in the description, why not? Again follow the guidelines as some directories won't allow promotional phrases such as "the best site in the world for widgets"... Also, there will be other sites on the same page, so their descriptions may have your keywords.
Should I mix up the title and descriptions on each directory? Or just use the same title and description on every submission I make?
Mix it up a little. No harm in using the same title several times, but not always the same. Also, I'd imagine you'd like to perform well on more than 1 or 2 keywords, so be sure to use titles/descriptions that include different keywords once in a while.
Check this thread.. it's an old one I've written about web directories faq.. Maby update it soon.. http://forums.digitalpoint.com/showthread.php?t=25101
Also, these days many guys are offering quality directory submission services at cheap rates. You may try them too.