How does the seed value work in Weka for clustering? I have recently been learning about the various clustering methods, and I decided to apply Furthest Point clustering in Weka with varying seed values. 

The seed value dictates the initial choice of points in the data set. It can't be totally random, since repeatedly doing the clustering with, say, seed = 3 gives the same result.

How does it select data points based on the seed?
Pseudo-random number generators are initialized with a seed.

There is little real randomness available. Most just looks random to us, because the pattern is too complex. Read up some examples on pseudo random number generation such ad Mersenne Twisters.