three coin method:

heads = 2
tails = 3

three coins net either:

2+2+2 = 6 = -x-
2+2+3 = 7 = ---
2+3+3 = 8 = - -
3+3+3 = 9 = -0-

where -x- is a 'old yin' line changing into yang - - > ---
and -o- is a 'young yang' changing into yin --- > - -

in the sixteen bead (or marble) method you need four colors:

7 black = - -
5 white = ---
3 red = -o-
1 blue = -x-

you draw one out and record the line then return it and select another.

the reason for this is that it maintains the mathamatical probabilities of the yarrow stick method whis is based on the 'golden ratio' whereas with coins you have a linear distribution of probabilities. ie, you are just as likely to get a old yin as anything else. in yin/yang energies it is more unlikely that yin (passive/receptive) would change to yang whereas it is yang (active/creative) nature to change.

the sixteen bead method preserves this tendency while being fairly quick relative to yarrow stalks. that is why i use it.

I looked for the seed method online to tell you about and found a lot more, check this out!

en.wikipedia.org/wiki/I_Ching_divination