Simple implementation of ELO Ranking Computation. Writeup in C# can be found here.
There is also a C# implementation available at Wally869/RankingELO-cSharp.
By creating randomly distributed pairs of (skill level, ranking) and making players "fight" the results seem to converge towards what we expected (x-axis is skill level between 0 and 1, while y-axis is ranking).
