[Doug]

Normally when I try to learn a song, I start with the chords that I get from a book or on line and then I try to find voicings for the chords that have the melody notes in them (or nearby). But how do you find the chords when you just have the melody notes?
As an example, here's a snippet from a well-known samba that has a chord progression as follows:
...Am7....Bm7b5.E7b9 notes for those chords as follows:
E..C...B.A.A.......G#.B (I tried to space them out properly)

But if I just started with the notes, how would I come up with that chord progression?

[Fretsource]

You probably wouldn't. Dozens of chords could be used in place of those and they'd all make the same melody sound different in their own distinct ways.
The writer has taken care to choose very colourful chords to capture exactly that special sound he or she wanted and probably even made a point of choosing chords that no-one else would be likely to come up with (but still matching the melody to some extent).
That's an important way to make music sound original - choosing a chord or chord progression that no-one expects.

For more on this check out Tekker's lesson on chord substitution - you'll find it very informative.

[Doug]

therein lies the art
Thanks Fretsource.

[Fretsource]

At the other extreme though, chords to most C&W, folk songs, and simple pop songs can quite easily be worked out from the melody, which is mostly just chord tones and passing notes. A lot of those folks don't take kindly to colourful chromatic chords like those above that are commonplace in Jazz, classical and Latin, etc.