A strong choice is one that is definite, clear, out where everyone can see it. It Commits you in a very definite way, so there's no turning back.
To make a strong choice, Be Concrete and take a definite attitude as you speak. Become a certain, specific person, not a generic person that could be anyone.
Compare:
"Hi, uh, how's it going?"
with:
"Our first trip to Washington State. Wow, wild green onions!"
Which do you think creates more illusion of reality? Which gives your scene partner more to work with?
See Commit.