How to respond to Influencers / Advertising / Collaboration requests?

Working a fairly successful drop shipping company at the moment and have been reached out to by a number of small time influencers (either insta-users or companies looking to advertise us in their magazine/page etc).

I was wondering if anyone has any insight into:

• potential questions we should asking of them;
• things to watch out for;
• websites with guides on the subject or the foundations for scripts for doing so;
• a more fitting subreddit for this question if this isn't it; or,
• a link to a previous post covering the above.

Thank you!