I'll be serious since you have been (somewhat) serious today. First it needs to be determined the exact reason the plane came down. All signs point towards a SAM at this point, so we'll go on that theory.
If it's the separatists, than the EU, Ukraine and Russia all should join in telling them it's over, lay down your arms and go home. No more fighting. If they refuse, then no holds barred, we give the Ukraine anything they want military wise and they clean house. The EU sets up a peacekeeping force when it's all said and done. Russia will not harbor the insurgents on their soil and will root out all the bases of operations. The separatists will give up, period, end of story. If Russia refuses, see items from below.
If it was a Russian (government) SAM, heavy sanctions, frozen assets of government and private individuals, they give up all claims over the Crimea and eastern Ukraine subject to an EU or UN peacekeeping force. The Ukraine is invited into NATO immediately and the border with Russia gets fortified. Reparations are paid to the Malaysian government as well as to all the families of the victims in an amount determined by the World Court. We start shipping natural gas to Europe as the EU cuts off the supplies. And the military leaders in charge of the SAM site will stand trial as determined by international agreement.