This is, word for word, an email I sent to one of my players after several sessions ended in Total Party Kills. A couple of their characters were very close to dying during this particular adventure and all of it could have been prevented with the advice below.
You're searching an ancient wizard's tower on the fringes of the desert, far from civilization and unable to recruit additional help. This tower has harpies and lizardmen and a manticore and possibly other even more dangerous encounters waiting to be discovered, enemies so dangerous that a group of inexperienced adventurers like yourself will likely all die attempting to explore the place. What can you possibly do to avoid dying horribly?
Always talk with the locals. Sometimes the local bartender knows a tale or two about previous explorers of that dangerous tower. If the bartender doesn't know then maybe the farmers on the edge of town know somebody who got close to the place. Maybe there's a hermit camping at the oasis just half a day away from the tower. Always find the people living nearby and ask them what they know. If they don't know anything then maybe it's written down. Check with a sage and see if they have a scroll or a book that describes the tower. Visit a cartographer and ask to see a map of the region, maybe there's a clue written onto the map he shows you, or maybe he knows a thing or two himself. Even if what you learn isn't entirely accurate, knowing an obviously false rumor can still improve your chances of survival.
Walk to the edge of town, find a nice secluded spot, sit down on the grass and close your eyes. Yes, I'm telling YOU to do this, not your character. Depending on how you interpreted "edge of town" you can either hear cars whizzing past or you can hear the faint echo of motors traveling along asphalt. Even if you're sitting at home, simply close your eyes and listen, you might be astonished at what you can hear within the ambient noise of your neighborhood. Sound travels, and the faster you move the farther the sound reaches. Now back to your character. Whenever you think there might be wild animals, dangerous locals, or monsters nearby then you should focus on being silent. Rampaging through that wizard's tower, smashing cupboards and flipping over tables with no regard for who or what might hear you can lead to you getting yourself killed, and anybody else who decided to follow you too. All creatures are attracted to sound and very often they will search out noises made by careless adventurers like yourself. On the flip side, you should be trying to listen for the sounds of nearby monsters whenever you can. This allows you to take careless enemies by surprise or even allows you to avoid a monster you'd rather not face altogether.
Exploring that wizard's tower slowly will allow you to explore it cautiously. Search everything, there might be secret doors along the walls, those chests may have false bottoms, and there might be a monster lurking on the ceiling of that room you're about to enter. Utilizing these secrets can also help you secure the treasures of this wizard's tower, if you find a closet that can only be opened by pressing two different tiles on the opposing wall then securing your valuables in that closet allows you to safeguard them for a later return. If you must make camp while you're exploring, do so from a distance. A secure vantage point that allows you to scout the tower from a distance before you even enter is best. Spend a day there and then you can learn if there's regular traffic, perhaps those lizardmen only come out at night, maybe they never venture farther than the first floor of the tower, and maybe they use a signal to let their brethren know they're coming back from a hunt. Spying on the enemy falls back onto the first rule and helps you to be better prepared. If you can hide a secure camp near your target that means you also have a good place to retreat to if the need arises.
Follow these rules, in the order presented, and you will greatly enhance your chances of survival. And if you don't think you can defeat a particular creature, then run away. Come back with friends, return with an army if you have to, but make sure you survive first. The treasure can wait if you can't carry it all in one trip.