Post a riddle, let others solve it.
DO NOT USE A SEARCH ENGINE TO FIND THE ANSWERS. Don't ask other people, etc. If you can't figure it out, tough. If a riddle lasts a few days and hasn't been answered, the OP of the riddle should provide the answer.
Here's the first one. A classic.
You're standing at the bottom of the stairs. There are three light switches, one of which turns on a light in a bedroom with a shut door (no light can shine beneath or around the door) on the second floor. Without going down any stairs, how can you determine which switch controls the light bulb in that bedroom?