This Card Force is one of the cleanest and most convincing methods I know of. The spectator can truly touch any card they want, and they always see the force card. Before you learn how to do this force, you will need to learn the spread cull. I have made a tutorial for this already and you can find a link to it in the related videos section.
This card control will take a good amount of practice to do smoothly and without hesitation. You will need to spend some time in front of a mirror to make sure you are angling the pack downwards a bit so that the culled card cannot be seen.