Dedicated Server basics – I’m a newb to it all lol

Here’s the low down of my discussion/question…
Me and some friends want to run a dedicated sever for online games, such as counterstrike etc, and what we would like to know:
Whats the best ‘deddy’ OS?
How much (in GBP) does it cost to maintain a server?
What upload speed would we need to have a good connection to our server?
What are the dedicated server basics such as how to run it, what we need to know etc.