I voted others. In the first year or two years(depends on how things go) i would increase the guerilla training and deploiment of special troops and the training of the south Vietnamese army. In those two years, i would try to ensure my forces the cooperation of native tribes, and of vietnamese. With these guerilleros, i would drop more and more special troops with choppers or river boats, depending the location and situation. I'd begin with South Vietnam territory, then toward the Ho Chi Min trail, then North Vietnam. The goal being to create havoc and confusion in Vietcong controlled territory and North Vietnam territory. I'll feed them with the kind of war they feed us.
After that 1st step, i would gradually increase military pressure. 1st on the Vietcong hideout in the South, then crossing the North border. I'd bring all the manpower possible. I'd built the mightiest logistic organisation possible. Because our troops would need loads of stuff. By increasing the military pressure, i mean the we push them Viet before us. After each week of advance, a massive camp would be built to support the push. By massive i mean with an airfield capable of supporting our choppers and even supply planes. After our advance, the South Vietnam would keep our rear secure. Note that above i mention South Vietnam troops training. I would also give them fire experience by incorporating some units within our OOB, all that depending of the opinion of my officers in charge of the training.
Once the south have been "cleared", we'll massivly invade North Vietnam. If all goes well, the North is already "soften" by our guerilla tactics. Note that before going north, we'll be sure the HoChiMin trail isnt funtional at all. I wouldnt make massive bombardement on the North, but maybe once or twice devastating drop to make an "exemple".
At first i wouldnt send troops in Cambodia or Laos. I'd fight there with special troops only. If no other option available i would enter these countries with my forces.
There's lots of stuff i'm thinking of, but you have the picture.
ps. sorry bout the typo