They are all important, so they are all numbered 1.  The list is below.  As you read the questions, ask yourself which you think is most important?  And, are you following the leads of others, or leading the followers?  Listings are the inventory of your personal business.  Do you treat them with the respect they deserve?  Do you have the same approach to your inventory that other businesses have? 

1. Will you have to go to the site to change the listing for price or status changes?
1. Will the content you place there help or hurt your own web site rankings?
1. If you add a listing, are you put on a mailing list?
1. Does the site link to your site or do you only get to show a phone number?
1. Do they direct their visitors to your site or to some elses - is there a fee?  Who else can pay the fee to get traffic?
1. How often can they change their terms for placing listings there, and what could the consequences be to you?
1. If you don't put your listings there, what do you lose?  What do you gain?
1. If you spent as much time learning how to get your site found better, would that be time better spent in the long run?
1. Can they remove your listings if they want to?
1. Is it better for your listings to be found, or your business to be found?

Here is a 2.5 minute YouTube about putting your listings on someone else's site.