Keep in mind that your decisions matter and will carry over to other games.
Do not get out of the Mako if you don't have to. If you are engaging larger enemies, like Thresher Maws, keep moving.
Investigate everything. When driving around planets try and stay toward the edge (you'll see a red like do not enter area) you want to stay just far enough away from that, that you can see it...this will allow your sensors to pick up pretty much anything in the search area. And collect everything you can, finding minerals will be one of the quickest ways to earn money.
Speaking of money, save it to buy the best weapon then armor you can. I use the assault rifle almost exclusively so I chose to upgrade that first along with my armor. If you decide to use something else like the pistol, etc upgrade that first.
That should be enough to get you going...lol