How to identify a random Hash?

[doubler]

I've been doing some hashing using some of the archived crack me if you can contests files. It's led me to wonder how it is possible to identify a random hash as a certain algorithm? I've found a few scripts online to help, but other than a few algorithms they help identify, even then its not 100% reliable. I was wondering if theres any tutorials or guidelines for identifying a hash other than process of elimination and luck?