Have a scout
A scout is a character who moves ahead of the party, looking for traps, listening for noises, and exploring possible routes forward. A scout protects the party from the following risks:
- Area effect traps: A scout can discover or trigger an area effect trap while the party is out of range, limiting or negating its effect.
- Ambush: Large groups of intelligent foes can easily surround or ambush an unwary party. A scout can often spot or hear these groups early, giving the party time to prepare for combat, or to retreat.
Scouting is high-risk, and casualties are common. But having a scout reduces the risk of a dramatic failure which wipes out the whole party.
Thieves, with their ability to move silently, pick locks and find/disarm traps are a natural fit for scouts. Because scouting is very dangerous, it also often falls to the lowest-level members of the party. Scouts, unless they have some kind of dark-vision, must carry their own light source. A hooded lantern is a good choice, but even with this precaution the scout is very vulnerable to detection and attack.
There are a few schools of thought on scouting doctrine. Each has strengths and weaknesses, and which one you choose depends on the kind of dungeon you’re exploring.
The Far Scout
The far scout travels well ahead of the party, at least out of earshot. The advantage of this approach is that the noise of the party moving around the dungeon doesn’t alert dungeon inhabitants before the scout can quietly detect them. It also means that should the scout be ambushed or killed, the party might still escape the encounter. The major downside here is that the scout is very vulnerable to attack. Encounters which the party would have no trouble overcoming might prove deadly to the scout on their own. Far Scout doctrine then is most effective in overleveled dungeons, or dungeons with large groups of humanoids.
The Near Scout
The near scout travels only twenty or thirty feet ahead of the party, just inside their lantern light. This means that the party can immediately support the scout if they encounter some low-grade threat, but the scout can still protect the party from most traps. Near Scout doctrine reduces the scout’s effectiveness at detecting and avoiding ambushes.
Hard entry
By default, the scout is doing what we call “soft entry” of rooms. Checking for traps, slowly opening the door, and retreating at the first sign of anything living in the room beyond. So what do you do when the scout finds a room with something or someone living in it? The worst thing you can face is determined opposition set up in a doorway, where whoever steps through the door is fighting three to one odds or worse. Worse, delay in entering an occupied room gives the defenders time to raise an alarm, to gather reinforcements, and to encircle and trap your party.
The answer is a hard entry. The goal with hard entry is to get your guys into the room as quickly as possible, before the defenders can ready weapons or take up advantageous positions. Everyone lines up in the corridor outside, best fighters in the front. The scout opens the door, stepping to the side as they do so. The fighters charge in, picking targets and fanning out, aiming to get out of the doorway as quickly as they can. If successful, the hard entry results in a round or two of free attacks on the enemy while they are still unarmed, possibly breaking their morale and leading to a slaughter. If it fails (most likely due to a forewarned enemy), the result is your best fighters fighting in the doorway at disadvantageous odds, but at least with a path of retreat open behind them.
Polite Entry
It's an experimental technique, but consider knocking on the door. If the room's inhabited, you'll hear their response, and either open potentially friendly negotiations, or else be able to prepare for hostilities. More research is needed on the polite entry to determine the correct circumstances for its use.