The Humanist UK website (link) includes a number of descriptions of Humanism and what a humanist is, but each Humanist probably has a slightly different personal view that fits with their particular world view. 

If we asked 100 humanists to define Humanism we would see 100 slightly different opinions but they would all contain certain points which would be common:

A Humanist is someone who sees themselves as either an atheist or an agnostic.

We have One Life and we should therefore make the most of it.

Follow the Golden Rule: Treat others as well as you would like to be treated yourself.

Use Evidence (Science) and Reason, combined with human empathy when making choices in life.