My own preference is to always capitalize “President” when referring to the President of the United States. Use capital letters for letter abbreviations (CEO, IBM, PBS), and for your company and/or boss. Because the capital letter indicates importance, use it when referring to the ones you wish to impress (or are required to pay tribute).
If you work for a government, you have my sympathies. You may choose (or be required) to capitalize the outfit: federal/Federal, city/City, state/State, army/Army.