I was an instructor in the Navy teaching Morse Code to potential Communications Technicians back in the early 70’s. One activity we found very useful was to encourage students sound out the code, either verbally or in their heads, whenever possible: When you see a stop sign, spell it out in code “dit-dit-dit, dah, dah-dah-dah, dit-dah-dah-dit. (stop first, of course). Do the same with a newspaper headline every morning, at work when you see a sign on the wall, the numbers on a clock, etc…. You get the idea. We found that students that used this technique learned the letters quicker than those who just put it out of mind until the next class.