Begin by choosing a participant from the audience, and have them see you place the sealed envelope, and the three coins on the table. Explain how in the sealed envelope, you have already predicted the outcome of soon to be events.
Let's say the 3 coins you will use in this trick are a Quarter, Nickel and a Dime.
You want to "Force" the quarter (or whichever coin you want)... so first you ask the participant to choose any 2 of the three coins. If they choose the Nickel and Dime, you ask them to push those to one side, leaving them with the Quarter.
If they choose the Quarter and the Nickel, ask them to push the Dime to the side. Then ask them to pick either the Quarter or Nickel. If they pick the Quarter, say "You picked the Quarter...that’s the one we will use." If they choose the Nickel, tell them to push it one side and say, "So now you’re left with the Quarter... That’s the one we will use."
See how a "Force" or "Magicians Choice" works now? :) No matter what they pick, in the end, they will always end up with your choice, in this example, the Quarter.
Now ask your participant to flip the coin they have "chosen" (the Quarter), and call out whether it's heads or tails.
Slit open the envelope to reveal the prediction -- slip your first and second fingers inside to open up the envelope. As you do so, push the middle divider you made from the second envelope back or forward depending on which prediction you need to reveal. Once the flap is in place, hold it there with your thumb and finger, then tip the envelope upside down so the correct folded prediction falls out. Ask the participant to read the prediction out loud, and while they do so... slip the envelope into your pocket.