2) the party should use their resources effectively so as to minimize risk and exposure -- if you've only got sufficient resources to last through four encounters, you want to get as much accomplished with those resources as possible, meaning if you're exploring a 60-room dungeon you don't want to just fight the first four monsters you meet, retreat to rest, and come back 15 times, but rather you want be strategic about it, to avoid or circumvent as many non-essential encounters as possible to maintain your resources for those encounters that are essential, allowing you to complete the dungeon in as few expeditions as possible -- a 60-room dungeon is likely well beyond the means of even a very careful and clever party to beat in a single expedition, but might be possible in 2 or 3, whereas a more careless party might take a half dozen or more (remembering, as above, that the dungeon is likely to get a little tougher with each new foray as the inhabitants react to and learn from the party's actions -- take too long, allow the bad guys too much time to react, and eventually the dungeon will become impossible (I've had this situation occur a couple times in my games)). So, a clever party will always be looking to run away from, sneak past, trick, negotiate with, or bribe minor/non-essential encounters so they can get past them without having to use up their crucial combat and magic resources; wandering monsters become the ultimate bane who should always be run away from and never fought, because they use up resources without accomplishing anything (you're no closer to your goal and have now used up 1/4 of your resources needlessly).
If you have a 1st edition DMG (and if you don't you probably should, for reasons just like this) there's a great essay (pp. 104-105) about Monster Organization and how monsters of various intelligence, alignment, and organization levels are likely to react to repeated forays by adventurers which should give a good idea of how to handle these sorts of situations (and emphasize the fact that, given sufficient time and foreknowledge, even a group of statistically weak opponents can challenge a much tougher party if they're of sufficient intelligence and organization).