I use the "Capitalise important words" convention in titles. My wife who tends to adhere to older conventions doesn't like it and usually tries to persuade me to change it to Capital only on the first word of the title. OTOH she is an excellent proof reader and tends to pick up on my little foibles like scattering capital letters all over the place where they are not appropriate.

I was taught at school that in poetry the first word of every line should start with a capital letter, (after all, what is a song but a poem with a tune) so that is what I do.