When I first started posting my interest in getting a snake here I was told that any of the snakes listed in this thread would be good for a newbie, I can't understand why everyone is having a go at his snake choices, hozy, if you want a diamond go for it!
Here are some questions I think you should be solid on before getting your snake:
1) What temp gradient should that species be kept at?
2) What humidity levels should be?
3) What size enclosure should it be kept in?
4) How much and how often should it be fed?
5) How should it be handled and how often?
There are probably a ton more things you will learn and do, but if know this stuff and you have a proper setup then you are ready, as long as you are prepared to do the regular clean up and monitor the enclosure conditions regularly then in the words of nike: just do it!
Cheers.