First you need to learn the difference between cover and concealment, because when you state using camouflage netting for cover that is not quite right, it would be concealment. Cover stops bullets concealment does not. Now more to the point of your question, you are missing to many details to give a great answer. Positions to fight from will be dictated by terrain, equipment and a few other details. If you are looking for materials to fortify with that will depend on funds, but sand bags and railroad ties are a good start.
"Intelligence is not the ability to regurgitate information. It is the ability to make sound decisions on a consistent basis "--me
"Just remember, when you are talking to the average person, you are talking to a television set"--RDJB
One Big Ass Mistake America