Actually I would say the best thing the west could do is nothing.
Why on earth would we want to risk turning a small local conflict over a nation that is next door to Russia into World War 3 and the destruction of us all. Its a shame that both NATO and the EU have allowed themselves to move eastwards since the end of the cold war irrespective of what former eastern bloc governments want. This expansion has not added to our security but has made things far more dangerous. We are now thanks to NATO committed to defending nations that just 25 years ago were totally in the soviet sphere of influence. Talk about a reckless policy. The question has to be asked what is in it for us, the western population at large?! Its not as if the former eastern bloc nations are military strong and could aid us much in the event of a future war, but on the other hand require total protection from us.
Going back to Ukraine, right now Russia is still their biggest trade partner. Its utter lunacy for us to get involved with this in any way, shape or form.