hashing is quite large subject. I myself simply use hash to confirm whether two files (or more) are identical or not (using md5sum, sha256sum).
But as the books say, hashing could has collisions. And hashing, one way or another, could be reversed. or in other word, there is no such perfect true one way hashing. Alright, we can't pursue perfection here. So what's the recipe to pick the best hashing method?
Fortunately, an article written by Valerie Aurora gives us the clue. For the impatient, you better use something like SHA-2 (sha256 or better). I found the article nicely explain the issues behind hashing with quite friendly (read: non hacker-ish) tone :)
Cheers and have a nice day ....