For starters:

- not eroding and breaking international law by invading Iraq, setting a precedent cited by Putin

- not signing the Den Hague invasion act

- not getting involved in various "revolutions" in the east, like Ukraine

- not targeting all russian people with sanctions after 2014, but only those in charge

You know, in general leading by good example. If we want a international law forbidding countries to invade each other - it only works if the law applies to everyone. This I would consider smart politics.