If you want to actually successfully operate, they you should (eventually) practice copying Morse Code at the full range of WPM speeds you expect to hear over the air. Most Morse Code practice software allows you to change the WPM, try from maybe 12-20 WPM for SKN (straight key nights) up to 24-40 WPM for CW contesting. If one practices on only slow characters, it will be hard (if not impossible) to copy at higher WPM speeds. This is likely at least partially true for the inverse as well. If you vary your practice WPM rate, you will likely be more successful once you get on the air.

For QSOs (especially for DX), don't forget to learn to reliably copy random callsigns, not just common words and abbreviations.

If you want to actually successfully operate, then you should (eventually) practice copying Morse Code at the full range of WPM speeds you expect to hear over the air. Most Morse Code practice software allows you to change the WPM, try from maybe 12-20 WPM for SKN (straight key nights) up to 24-40 WPM for CW contesting. If one practices on only slow characters, it will be hard (if not impossible) to copy at higher WPM speeds. This is likely at least partially true for the inverse as well. If you vary your practice WPM rate, you will likely be more successful once you get on the air.

For QSOs (especially for DX), don't forget to learn to reliably copy random callsigns, not just common words and abbreviations.