Best way of learning the aviation alphabet?
Presuming you're referring to the ICAO Alphabet* , (alpha, bravo, charlie, delta, echo, etc.) the easiest way (in my experience, from learning it as a disambiguator for phone work) is repetition, same way you learned the alphabet as a child, or the same way you'd memorize a poem.  Get a written list of the letter names, read them through several times a day, and over time, start reciting without reading.
Do this several times a day for a week, you'll be close if not there.  A second week and you should start to think in phonetic alphabet.  A third week and you'll wonder why everyone doesn't think in phonetic alphabet.
*corrected from comments, originally International Phonetic Alphabet, which is a whole different thing.