Reply to Dropping a sample right before a drop to spice things up?

I don't know if a lot of DJ's do this, but it seems like dropping a sample right before a drop is what samples were made for. Do you guys do this? Is there an art to it? Is there a way to make it work every time? Dropping vocals or something from a popular song right before a nasty drop just seems like it would really increase the energy level. Even doing a backspin sample right before the next track comes in could be really cool. What do you guys believe?