After some study of instrumental composition, one wishing to pursue composition, would inevitably come across the human voice and choral composition. Just as a conductor cannot ignore opera, a composer cannot ignore vocal pieces.

How to learn it? First, are there any suggestions for books, resources, etc.? Any tips, advice? Then, how does one fit lyrics to music. Do you write the lyrics first or the music? How do the syllables fit with the beat of the music? How does one combine multiple voices and lyrics at once? Please leave any comments or ideas. Thanks

Join a community choir and go to hear a lot of choral performances. I worked for a local youth choral organization for a few years. Choral music is a different animal and is best studied up close and personal. Some composers to look for:

Randall Stroope
Eric Whitacre
Gyorgy Orban
Morton Lauridsen
Caldwell and Ivory (for something less obtuse)
Nick Page

Check out the offerings of choral publishers, Earthsongs and Santa Barbara Music Publishing being two good places to start.

Probably where to start with the music would be Bach 4-part chorales from your theory classes, getting a sense of smooth voice leading.

Most choral music is written to an existing text. It might be good to figure out the general rhythm of simply reading the text - then the rhythm of the music will make a little more sense.