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Your first step to survival in Signs of Life is to build a shelter. This can be as primitive as hollowing out some space in the ground and place dirt or another block to cover the entrance so you don't get creepy crawlies messing with you. Fruit is fairly abundant, and can be collected by holding the MMB over the fruit (or selecting the light blue MEG Tool which is your Grab Laser). Stay full, you get a well-fed bonus.
Suicide is an Option
If the Respawner isn't nearby and you cannot locate it easily, it may be in your best interest to map your current location, then suicide and build your shelter near the respawner. Despite the fact that you start with a pistol and a flare gun, your ammunition is extremely limited, so it's really not that big of a loss. Additionally, the structure with the respawner is likely to have tools and containers that will prove to be more useful in your first few hours.
To build a Campfire, you need Sticks and Grey Rock. Use your MEG Tool to remove the block beneath a tree and the whole thing comes down a lot easier than using the MEG to cut the tree itself. Collect the materials that drop. Grey Rocks are a little difficult to find on their own, but if the base the respawner is in has a Pick, you can use it just smash the abundant rock formations to get them. You'll also need to craft a Firestarter, which uses Grey Rock and Flint.
Back to the Smelter - you'll need Clay, which you'll have to dig a little for. It's fairly abundant just below the surface, as is Flint, which you'll need to make your Firestarter. If you suicided and got the Pick, you'll find that it makes digging a lot easier since it doesn't need energy like the MEG. (Picks tend to hit blocks above you and all around you if you're tunneling. RMB makes it slightly more controlled, but it's not enough to tunnel. Use your MEG if you need to make precise cuts.) Once you have your 20 Clay and your Flint, head back to your base and get your Campfire going with the Firestarter. (Be careful, you can set grass on fire with this thing. And while the campfire won't hurt you, wild fire will.) Stand near the lit Campfire and you'll be able to make your Bricks. Finally, you can build your Basic Smelter.
Now start mining. The first things you'll want to find are (in order of priority): Coal, Copper, and Iron. FYI, iron is a little deeper than the other two. Once you have Coal and Copper, you can craft a Saw (requires 1 Copper Ingot), which will allow you to make Wooden Boards.
Go ahead and make a few Wooden Boards, even if you don't think you'll need them right now; it opens up recipes, most notably a chest to store items. Recipes are discovered when you either pick something up or craft something. You can have all the resources in the world, but unless you discover the recipes, you won't be able to build the more advanced items. Replacing the lens in your MEG would make a good a first project.