I have read "How to become an editor", but what are the qualifications and how long does it actually take to review and approve a site for the directory?
The ability to read and comprehend editing guidelines.
The ability to look at a web site and quickly distill its unique contents into a fairly short description.
The ability to accept input from other editors without getting all huffy.
The abiity to work well with others and play nice in our internal fora.
Curiosity helps.
Gud speling and gramar and teh abiliti to prufread also helps.
As far as time commitments: it is up to you. We require one edit every for months in order to remain active, and while some submitters somehow this that this is somehow unfair, we find it works well. It can take from 2 minutes to more than an hour to review a site. When I first started, it took about half an hour on average, but with experience I got a lot faster. There is a lot of reading that should be done before one's first edit -- but not everyone does that.
Attitude is important. People should join ODP because they want to help out. People who join to game the system and only list their site are usually quickly found out.
People who want to increase their chances of being accepted should view the application as a form of professional examination. Read the instructions, give a lot of thought and care to the preparation of answers. Really research the three sites and write stunningly good titles and descriptions that comply with the editing guidelines. I have talked to many new editors who say they spent upwards of two hours on their ODP application. That experience is similr to my own. Plus, it is not like it is the only time you will see that form. It's twin sister is used every time you want to apply for additonal categories.