Cast a hexagram
Hold a question in mind. Throw once for each line, from the bottom up; the lines that come up old (6 or 9) are the ones that change. Or let the moment itself make the figure, the Plum Blossom way.
Each throw here uses your browser's cryptographic random numbers, not a seeded sequence, and shows the three coins it came from. With three coins the chances are 1 in 8 for old yin (6), 3 in 8 for young yang (7), 3 in 8 for young yin (8) and 1 in 8 for old yang (9).
Four questions people ask about the method
Are the coin values right?
Heads count 3 and tails 2 by convention, so three coins sum to 6, 7, 8 or 9. An odd sum is a whole line, an even one a broken line. 7 and 8 are lines at rest; 6 and 9 are old lines, the ones that change. Which face is heads does not matter as long as you keep to it: the four sums come out with the same chances either way (1 in 8 for a 6, 3 in 8 for a 7, 3 in 8 for an 8, 1 in 8 for a 9).
No line changed. What does that mean?
Read the hexagram as it stands, Judgment and plain reading, and leave the lines alone. An unchanging hexagram is the most settled kind of answer: the situation is what it is, for now, with no particular line singled out. With three coins it happens about one cast in five.
I got the same hexagram again.
With 64 hexagrams, a repeat within a few casts is not rare, and the tradition reads a repeat as emphasis, not error. If you asked the same question twice, the text of 4 蒙 has the classical answer: the first asking is answered, the repeat is not. Change the question, or sit with the first answer.
Do I read the second hexagram?
Yes, but after the changing lines. The order is: the first hexagram for the situation, the statements of the changing lines for the specific part, then the second hexagram for where things are heading. The second hexagram's own lines are not read. If several lines change, the changing lines still come first; some readers weigh the upper of two, others read all of them in order.