Can Arthur Somervell's advice be bettered?
"To those amateurs who wish to sing National Songs with musical intelligence, and to give pleasure to those who listen, and who cannot go to a really musicianly teacher of singing to learn each song, I should recommend that they should
(1) carefully look at the tune and words, and determine what is the leading idea running through the song. Is it, as in " Scots wha hae," a battle march, or as in "Mary Jamieson," a love lament; or as in "The Tree in the Wood," a mystic, dreamy legend ? Let this leading characteristic dominate the whole rendering of the song.
(2) Get the rhythm well into your head, and play over the song to yourself in such strict time and rhythm, that a village audience could stamp its feet to the tune; and afterwards, never forget this rhythm, even during a rallentando.
(3) Then study carefully what scope is given in the tune and the accompaniment, to express the changes of sentiment of the words.
And finally always think of the song as a whole, and do not exhaust your effects before the final climax, should there be one. Then within the limits of time and rhythm, put into your singing all the expression or feeling you can give.

Remember that the scope for feeling is limited, and that therefore the expression of it is best given by a few delicate, forcible touches.
It is hard to say exactly in what expression consists. It is easier to say that it is not in absence of rhythm, it is not in entire absence of time, it is not in violent emphasis of unimportant notes or words ; in a word, it is not in the vulgarity of extremes."