I don't believe you salute until the guy is sworn into office. If you saluted before, that would be like saluting an officer who had not been commisioned. Of course, even after his term is up, you'd still be required to salute the guy, following protocols similiar to a retired general / admiral...

You are not required to do this generally. "From United States Army Field Manual FM 22-5 The rules of saluting are as follows: When you meet someone outside, salute as soon as you recognize an officer (when about six steps away). Salute all officers (recognized by rank) in official vehicles identified by special plates or flags. Salute only on command when in formation. If in a group and an officer approaches, the first soldier to recognize the officer calls the group to attention and all personnel salute. If you approach an officer while you are double-timing alone, assume quick time march and render the hand salute. When the salute is returned, execute order arms and resume double-timing. The salute is always initiated by the subordinate and is terminated only after acknowledgement by the individual being saluted. Accompany the salute with an appropriate greeting, such as, “Good morning/afternoon, sir/ma’am.“ Salutes are not required to be rendered by or to personnel who are driving or riding in privately owned vehicles. It is not customary for enlisted personnel to exchange salutes, except in some ceremonial situations. Never render a salute with a noticeable object in your mouth or right hand. If you are on detail and an officer approaches, salute if you are in charge of the detail. Otherwise, continue to work. If you are spoken to, then come to attention. All Medal of Honor recipients are to be saluted by everyone in the military, to include the President of the United States. Saluting is generally prohibited in field conditions, as it could help an enemy identify officers." Source and further information: http://en.wikipedia.org/wiki/Salute

You are not required to salute former Presidents nor are you required to salute former officers, no matter their former rank. Once you leave office or sign your discharge papers, you cease to be part of the chain of command and/or a member of the uniformed military forces. If you are a candidate for President, you are not part of the chain of command. You are not entitled to a salute.