For testing purposes (NOT real life purposes) - Step 1 - Read the Rules. Read them again. Read them while trying to memorize them. Write them out to see how far you’ve gone in memorizing them. Read them again. Try writing them out again. Repeat until desired effect is achieved. Step 2 One month before you take the exam, get the Murphy’s books, take Rules questions book - go through that book EVERY DAY at the end of the day and ONLY read the correct answers (high light them before you start)- you’ll be able to answer the questions before you even read them all the way through. Do not use any computer based test prep for this - go straight for the hard copies.
For actual, real world understanding - See step 1 above. Read Farwell’s Rules of the Nautical Road cover to cover. Yes, it’s dry just do it. Get experience through simulators, and pay attention and haul the Rules out during watches - teach/quiz your ABs. Repeat as necessary.