Get Scouts to come up with what they think the lines of the Scout Promise and Law mean in their own words
Hand out blank copies of the Scouts Promise and Law and ask Scouts to come up with what they think each line means in their own words, get them to try and use words that aren't already in the given line (eg. what does "duty" mean, or what does it mean to be "loyal").
Then you can hand out a copy with some dictionary definitions of some of the words.
Finally ask the Scouts to come up with several examples of how they have kept the Promise and Law (based on their understanding) and maybe ask each Scout to share one of their examples with the rest of the troop.