1
I need to tell you something.
To sign this, start with your index finger at your lower lip. As you express that you have something to share, rotate your hand and point the finger outward directly toward the person you are talking to.
2
Please tell him the news.
When signing this, the movement of the word 'tell' is directed at a third party. Start at your lower lip, but move your index finger outward in the specific direction of the person you are referring to.
3
Did you tell them?
Begin with the standard starting position at your lower lip. Then, instead of pointing straight out, sweep your index finger outward in a slight arc to represent telling multiple people at once.