Most of my tips are already posted.
Make sure you get everyone on the network, which for most is just 3 stars.
Use your robots to deliver stuff. You have best results when you have completed roads between you and the receiver. You will need to go to the person in order to trigger them joining the network and when you get all 5 stars, if you do that.
When you get the mission about the dead body, just before you cross the tar lake, make sure you don't kill the MULES in the area or you will have a void out. Also, complete this mission, or you will have a void out.
Once you cross the tar lake, you will be returning to the previous areas, so don't stress out over missing somethings.
Despite what you are told, the return trip doesn't have to be a massive rush. Slow down and be prepared for the next area.