One way I find makes it easier to remember is, if you have your hotkeys set up Ten>Chi>Jin, then single target is always left-to-right, and AOE is always right-to-left.

• Raiton = Start at Ten and push 2 mudra total going left-to-right (Ten->Chi).

• Hyosho Ranyu = Start at Chi and push 2 mudra total going left-to-right (Chi->Jin).

• Suiton = Start at Ten and push 3 mudra total going left-to-right (Ten->Chi->Jin).

• Katon = Start at Chi and push 2 mudra total going right-to-left (Chi->Ten).

• Doton = Start at Ten and push 3 mudra total going right-to-left, looping when you reach the end (Ten->Jin->Chi).

Huton doesn't really fit, but you should only be using Huton pre-pull anyway so that doesn't matter.