Pay attention to your oxygen level
If this isn't the most important thing to know when playing Shinsekai, then it's certainly up there. Your oxygen essentially plays as your health. There is a booster that allows you jump higher and faster, but by using this, it will cause your oxygen to drain.
This is the main way to get your oxygen used up but it is necessary on many occasions (and it's fun to use). The other you'll get killed is by getting crushed by ice like we mentioned or getting killed by an enemy. A foe will do so by cracking the glass on your suit
You already know what happens when your suit is destroyed. Grim Reaper time. Fortunately, early one it's pretty easy to fend off enemies. It's just a matter of carefully using the boost and escaping the ice that's chasing you. Remember: oxygen is health.
Yes, I know you're trying to move at a fair pace to avoid the ice, but while you're moving, try to pay attention to your surroundings. There's a possibility that you may find something of great worth. It could be a much-needed oxygen tank or even a new weapon among other things.
Grabbing oxygen tanks will basically add an extra health bar to your character. Or it might be one that refills your lone tank. And the weapons you find can be very useful. One you will encounter early is like a gun which obviously is great for long-distance enemies.
Normally, you whack creatures with your melee weapon. But, once you find the long-range weapon, that'll make things easier when trying to kill enemies in awkward positions. So, have yourself a keen eye while on the move. If you don't have time, then don't sweat it and move on.
Make sure you save
This kind of goes back to being observant. As you explore, you'll see some save points that along the way. Make sure you save at these locations. You can't just pause the game and freely save. The only way you can do so is by finding these checkpoints.
The hope is that you don't die before finding the next one (unless you didn't get far from your last one). That's always pretty annoying when you have run, climb and fight your way to the checkpoint that you were so close to. This actually happened to me.
I was a little too slow on one of my climbs and I saw an oxygen tank that I wanted to grab after I climbed up. The savepoint was right in my grasp until the ice-carved me for a slow, painful death. This, with the checkpoint still being seen and it was oh so close.
So don't make the same mistakes I made. Save this game every chance you can get.
Balance your weapons
This one is all up to you, but it might be good to balance your weapon uses. This is because most weapons need to be crafted and are limited in use. If you are able to, use your melee weapon to tackle foes as this, of course, has no limits.
But it's understood that you want to get to enemies that are out of your reach. You can fire whatever ranged weapon you may have. Just make sure to be fair about it. Now, if you run out of ammo, then that's OK, you'll eventually find some other drops that will help you.
But, for early on, try to be wise if you can. If you do, then you'll be carving right through foes no problem (depending on the difficulty level you choose). It's always pretty satisfying to use any of the weapons in Shinsekai so have some fun with them.