- It's worth completing the Orders (seen by pressing L2). These give a big bunch of medals by, usually, doing things you'd be doing already, but you have to make sure you're going to the right planets for them.
- Always use your strategems, don't try to save them for 'the right time'. There's rarely a reason to enter an outpost without at least a couple orbital bombardments clearing out some of the targets inside. Get a heavy weapon down ASAP, thrown down sentries whenever you think you'll be fighting a lot of enemies, etc. The cooldown for them is never particularly long, and the effort you'll save for a well-placed one will far outweigh having to wait for it to return.
- Sub-objectives will rarely show up on your map ahead of time, so keep an eye on the horizon for interesting-looking structures like radar dishes, large buildings, etc. Some sub-objectives will give you a benefit for that mission, such as revealing points of interest or giving you use of a limited number of artillery barrages.
- Communication is important, but if you don't want to use chat, make sure you're at least tagging things of interest that you spot.
- Teamwork is also key. Don't put sentries where they're definitely going to shoot teammates, share the resupply drops and other ammo pickups, keep an eye on each others' backs.
- You can find premium currency and medals out in the environment, so always keep a lookout for points of interest. Similarly, if you see what looks like a shipping container buried underground (usually with some pickups outside its door), you can blow its door up to find some loot within.
- Holding the reload button brings up firing options for the held gun - semi/auto, rate of fire for machine guns, etc.