Skarpi, I've used all of the ways mentioned. Another is to play the piece over and over and over (if you can) and sing along with it each time. People around you, like wives and friends and family, will eventually learn the song too (if they don't do you a violence first).

As for the order of the program, you have to determine that.

Also, you have to sing the songs in order for the words to stay fresh in your mind. If you don't sing a song for a few years you might find that you've forgotten some or all of the words.