In my battalions experience if you want to survive follow this list
Make a secure base where it is nearly impossible to get ambushed and it can be easily guarded and easy to escape from for your team (this can also be hidden or a quick spot for ammo refills and supplies
The gun you choose is also good for battle carry a reliable weapon that wont let you down (Raider,Long-Shot,Long-Strike) and a side arm for emergency's (Dart Tag Pistol,Nite Finder,Maverick)
Carry ammo for a few rounds always keep clips load and ready for a quick reload
Keep communications open cell phones on vibrate work great for meeting points and strategic advice
If close combat weapons are agreed to keep a Nerf sword handy or a gag knife
never leave a teammate behind you will need all the help you can get