It is good to complete this mission exactly as described below, especially considering the fact that it is rather linear. Sticking to the method described in this guide will allow you to complete all three optional objectives and obtain the S rank.
Right after you land, start running towards guard post number 07 located to the north-east from here. Don't try to sneak through the guard post, but instead quickly circle if from the east and then from the north. Your destination is the truck shown on the pictures above, parked in the northern part of the camp. The Intel Team Member, who you have to rescue, is heading its way.
The best way to quickly complete this mission is to prevent the Intel Team Member from stealing the truck. If you've managed to do that, go to the description of the best way to extract the character.
If you failed, the target will start escaping using the truck and there are two things that can make the mission much more difficult now. Firstly, the action can alarm your enemies and make them chase the truck. Secondly, your ally will eventually have an accident and will be wounded. If you don't want to start the mission again, try to catch the truck and stop it (shoot at the wheels or block the road) before the accident.
At the end of the mission, you have to extract the Intel Team Member. Don't summon a helicopter, but leave the mission area using a truck or a jeep instead. You can steal a jeep from guard post number 07 and place your friend inside. Make sure that there are no enemies around before you enter the vehicle.
If you've don everything as described above, you will complete all three objectives (rescuing the ally, preventing the accident and leaving the mission area by land).