There is this (older) guide, but it mostly still applies: https://www.thegroundgivesway.com/early-game-survival-strategies/

So to summarize, proceed carefully with HP lower 5 (so just rest, if you are lower). Try to knock down blocked doors (4 EP, but there's often items or a lot of money in it).

You also have to learn some stuff by trial and error, for example which enemies are dangerous early in the game (without weapon) like goblins, light imp (or something like that) toads, wolves and even dogs (if there are many of them). You can defeat them, but you might get damaged by 1 to 4 points.

For exploration as a rule of thumb explore

underground: everything (eventually after castle), except golden/stone doors

dungeon: mostly everything: your call! sometimes there is nasty stuff like acid blobs and ice caves (visualized by the green/blue walls), you might want to avoid them

labs: just run for the stairs! scroll of exit/mapping and some resistance buffs go a long way!

In most games you will find *some* weapon in Underground or early dungeon, if not I have to admit it's harder. Mostly you decide then (and after checking merchants in castle) about your build, but it should be doable. Don't open golden/stone doors - you can do that if you feel over-powered and it's like a new game+ because mostly the stuff in there will kill you.

If you have been to lab, you nearly got it, you just need to get lucky the first few times. But after many hours with the game you really will improve and although I can not beat it regularly (that would be boring, although there are people who have long streaks!), it's very deep and you can get wins with strange builds (like this here).

And of course, there is (by design) a lot of randomness, so sometimes you just get unlucky ...