The first mission sends you against a North Vietnamese airfield. It's guarded by 2 SAM (Surface to Air Missile) sites which will give you a bit of unwanted attention! Take them out by destroying the radar units. See the AGM-45 Shrike checklist. (coming soon)
The MiGs are lined up very nicely... a tempting target for strafing practice! Some MiGs will appear on the scene but they're not too aggressive. This is a good opportunity to practice your dogfighting tactics. In general you'll do best to try and emulate the real-world tactics used in this conflict by fighting an energy fight.
That is... don't try and out turn the MiGs in the horizontal. The MiG21 and especially the MiG-17 can turn much tighter than the F-105 or the F4. Use the vertical plane of manoeuver.
Keep your speed (energy state) up and pull into the vertical when a MiG tries to turn inside you. If you try and turn with the MiG you'll likely end up in a lag pursuit, unable to bring the guns to bear and worst of all... low, slow and in bandit country! Here's an F-105 going vertical (in the background) after getting a gun hit on this MiG21
Now, having gone "over the top" and converted it's kinetic energy (speed) to potential energy (altitude), the F-105 merely has to continue to roll inverted, pull back on the stick and let gravity assist!
Now, if you were to miss again, use the built up speed to either "extend" for a missile shot or go vertical again and reposition for a guns or an AIM-9 shot.