Well...you really can divine with anything!
I wrote a book about it (called "Totalmancy"... which I have been too chicken to publish.) But I do love all the traditional "mancys" out there.Some are hilarious! edit...I have tried almost all of them at one time or another!
I would put various divination methods into *almost*the same few major catagories as you do Milfoil...with some sub catagories in each.
Pattern Divining (seeing patterns that form pictures or shapes, that are then interpreted through symbolism) examples... egg, oil, tea leaf,Coffee, bones, stones, smoke, toothpicks, M&Ms...(I would include compass, ouija and pendulum here too, as a subcatagory)
Oracle Divination (relying on indices, a pre-thought out system, or titles that have symbolic meaning) examples ...dice, dominos, tarot, oracle packs, drop stone lithomancy, IChing, runes, witches runes, oghams etc.
Scrying /Guide Work(tapping into the subconcious, or help from spiritual entities to receive sensory messages that can be interpreted.)
examples...guided meditation,vision quests, biofeedback, dream work, astral projection, or mediumship OR...Scrying... (seeing projections of images(or sounds)with the help of tools) such as crystal balls, mirrors,crystal bowls, water, fire, smoke..bibliomancy, automatic writing and spirit art have a sub category here as well.
(I combined these two categories because I haven't decided where these projections originate from...sometimes it can be our own subconscious, sometimes it might be something Else...even using the same methods)
Omen Divination(observing one's surroundings,nature and natural or unatural occurrances taken literally or symbolically) examples...weather changes, sky color, animal apperances, or behaviors, bird augury, finding objects
This isn't perfect, or course...because some things can fall into several categories depending on how the method is done! And some methods can arguably be placed in different categories depending on the person..
I would love to hear what others think too!