I have a friend that I show pictures from this site to, but she's kinda nervous when seeing stuff that's explicit. Is there a way someone can make it so that your searches only bring up pictures that are labeled as safe or questionable?

Use rating:s as one of your search tags.

Go to your profile, then go to settings and then in black listed tags put this; rating:explicit
and all the explicit stuff is not going to show.

Alternatively, there's Safebooru. Blacklist tags as needed.

http://safebooru.donmai.us

Thanks!