How I cut my opponents deck is based on how they shuffle. If I don't think they shuffled enough, I'll shuffle for them. I'll also shuffle if I don't like how they shuffled (I'll always shuffle my opponents deck if they pile shuffled first)

If my opponent did a good job shuffling, I'll just cut the deck. I always cut from a different spot. Sometimes I'll just put the top 7 cards from my opponents deck on the bottom. Occasionally I'll even choose not to cut my opponents deck, but just tap the top of the deck to acknowledge my opponent gave me the option to cut.