Practise copying from ready-made word lists (including CW Academy Beginner and Basic), upload your own, or pick words from a dictionary to focus on your problem characters.
There are many keyboard shortcuts which can also access additional functions. Press ? to list them.
To provide for a lot of different learning styles this tool has a lot of flexibility.
Fundamentally, you should choose whether you want to know in advance what Morse code you are about to hear. If you do not want to know what Morse is about to be played then it's recommended to hide the text or the whole soundboard and use "Shuffle" as otherwise you can start remembering what's coming up next.
If you are head-copying then choose one of the "Show and Say After" options so that you can check your answer. You can adjust the "thinking time" to suit your speed. It's fun to see if you can say what you heard before the computer does!
If you are writing down what you've heard then you can check your answers against the "History" panel and "Clear" it ready for your next session.
You could find a friend to practice with, turn off the repetition, flashcard and speech and just have them tap on the items in the soundboard for you.
With the speech facility you can practice on your phone with headphones or in the car, with no need to look at the screen.
For example to shuffle the entire list in the style of the Morse Code Ninja resources: ignore (1); set count to 1, 2 or 3 in (2); turn on "Say it" in (4); turn on Morse in (5); and turn on the bell in (6).
To play the list in order indefinitely when you want to know what you are about to hear, try: turning on elements of (1); setting the Count in (2); and consider using the bell in (6).
As with the other tools on this site, the timing is fully flexible. You can use the "Character speed" and "Farnsworth speed" settings for basic control, but if you want full control then toggle on "Advanced timing". With the advanced controls you could for instance just increase the space between words without increasing the inter-letter spacing (as Farnsworth does) and also adjust the start-up delay which may be used to resolve audio glitches or provide a pause after pressing Play before the Morse begins. Please note though that these timing controls only affect the timing of the Morse within the "2: Morse" section of the sequence. Gaps between sequences are controlled with the "Thinking time" and "Morse gap" times.
This tool works in most browsers: please see the FAQ if you are having problems.
Thanks to Glenn and Tom for their advice and testing.
I'm already aware of and working on these issues: