Don't waste your keys - used to unlock shelters and tunnels - early on. Abilities are timed and will run out right when it gets harder. Increased difficulty also means tunnels are more valuable, so only use them then.

Play it safe, particularly late on (it's frustrating to fail when you're doing so well!). There's no need to rush, in most cases.

If you need to, study guards' paths. You can do this fairly easily without the necessary ability.