The world of your campaign is a world, but it's also a world inside a game. As such, occasionally things that occur within it cannot be handled in a purely narrative manner. This is an index containing the mechanics of how actions outside of combat might have direct, quantifiable impacts.
AMBUSHES
If the party sets up an ambush of some sort, and it is successful, they should generally be rewarded with a preemptive round or a back attack in the ensuing combat.
Preemptive rounds allow combatants in a position to take advantage to begin with 30D - SPD instead of 50D - SPD. Back Attacks have this effect and also leave the monster force in a terrible formation at the start of the battle.
Ambushes generally require a skill roll of some sort, unless they are particularly ingenious. Under the talent system, Stealth and Huntsman are generally applicable. If the enemy force is lured in under false pretenses, it generally falls under Swindle, if traps are constructed, it might fall under Sabotage or Tinker, and these might inflict damage at the beginning of a battle.
Intelligent enemies caught in an ambush that will sufficiently trivialize the ensuing battle may surrender immediately.
DAMAGE
If you wish to inflict damage to the players outside of combat - for example, for stumbling into a jet of flame, or for falling through a pit - 100 x Tier is generally noticeable, 200 x Tier is vicious. If you inflict it to the entire party, halve it.
If you're inflicting it to monsters, 200 x Tier is considerable and good for inflicting to a single tough target, or almost taking a target out of battle. 100 x Tier is acceptable for the entire group. These are the values used for trigger actions, for example.
ENCOUNTERS
Whenever an enemy group decides to attack the party, or the party decides to attack an enemy group, combat begins, as everyone leaps into action and the matter of order is settled by speed and reflexes. This means that "simply deciding to attack first" does not grant an ambush.
Monsters often decide to attack the party, of course, traveling in mixed packs. It is often seen that the foul beasts of worlds share a strange, unnatural kinship, and it's not strange to see birds, poison vines and bears fighting together in unison.
As statuses typically don't exist outside of battle, enhancements can't be applied before fights.
HEALING
After a battle, the party will usually have taken some wounds and will often have spent some MP. While in the field, they can recover between encounters using recovery items and Spells.
Recovery items may be used freely outside of battle, even in the barest respite between fights - Potions and the like restore HP, Ethers MP, Phoenix Downs for the recovery of the vanquished, and so on. Statuses other than KO and Stone dissipate after battle, so there's no need to apply Antidotes. Note that many support abilities which benefit Item use do not function outside of combat, such as Stash and Potion Lore.
Spells may be used outside of battle to recover the party, but other abilities may not - this is due to the fact that many abilities exist such as Recharge and Life Song which would trivialize the whole process. (GMs that find this rule annoyingly arbitrary - because it is - may as well grant the party full HP and MP after every fight to save the characters the trouble of repeatedly Recharging after each encounter)
REST
When characters get a full night's rest in a decent bed, restore them to full HP and MP, and remove any statuses if they bear them. If they're paying for boarding, they generally pay a flat rate equal to 20 x Tier gil, basically a pittance. Tents and cottages have a comparable effect, so inns should always be considerably cheaper than them.
In, say, a fashionable resort town, feel free to have it cost as much as you think the player market will bear.
REWARDS
If you wish to grant awards to the party outside of combat - for an adventure well done, as the money found in a chest, to keep the leveling moving between voyages, or what-have-you, 500 x Level EXP to the party will level them up. 300 x Level EXP will generally feel close to what a normal session grants. Gil awards are generally expected to be a quarter of EXP awards.
If you award EXP without awarding Gil, the party's belt will tighten and they may feel less prepared going into the next tier. If you award Gil without awarding EXP, they'll be capable of spending more freely.
As for AP, a party will typically receive 25 AP per [300xLevel] EXP they gain, more in larger parties and less in smaller parties.
A simple session award would then be:
Level x 300 EXP,
Level x 75 Gil per party member,
20-30 AP.
If you're awarding treasure, A chest containing Level x 100 Gil would be an appreciable boon to a party, Level x 200 would be impressive.
TRAPS
If the heroes fall prey to some trap, they may either take damage or begin the next battle affected by a status effect.
Traps can range from the natural and simple - falling rocks, the webs of spiders, the threat of lava below - or to the elaborate and mechanical, like ancient alarm systems or pitfalls laced with alchemical concoctions.
Simple hazards can usually be recognized and avoided by means of Navigation, well-hidden traps can usually be detected by Insight. Danger Sense is always applicable, though it might not give any insight as to what the trap is - just that it'd be a bad idea to move forward.
They can also, of course, be simply avoided by the players recognizing the telltale signs of the trap and deciding to steer clear, and in practice, this route will probably be the most satisfying for all involved. Players might remark upon a strange description and ask for a skill roll to discern the meaning of it - that's perfectly fine.
The consequence of traps might be an ambush, back attack, or simply an encounter with especially difficult monsters. The trap might inflict damage (100 or 200 per tier, halved if it's to the whole group)
A trap might inflict a status effect, like poison or imperil. Typically, statuses don't exist outside of battle, but if affected by a trap, characters would simply gain that status as they enter their next combat. (If they have something that would cure the status on hand, like a Remedy or an Esuna spell, they can apply it before the next battle begins to avoid ever suffering its effects, as long as the trap doesn't set monsters upon them as well.)
SANCTUARIES
Even within the most fearsome of dungeons, travelers occasionally stumble upon a place of safe respite - an out-of-the-way cranny like moogles prefer to hide in, or the one chamber in a tower that the monster infestation cannot reach, due to its protective wards. It could also simply be a room whose door can easily be barricaded.
While traveling out in the world, a similar effect can be had if the party sets up camp-site to rest at.
In such a place, characters are capable of using either a tent or a cottage to rest - the next morning, their HP and MP are restored according to the item.
In some places in the world the party might discover the waters from a healing spring. If imbibed from the source, the water restores HP and MP to full and removes all statuses after a moment of rest. This water is pointless to bottle, or otherwise contain - though, somehow, some ambitious scholars have been able to, with great difficulty, make use of its powers elsewhere by carrying it about in a lidless, wooden bucket.
SHOPPING
Whenever someone visits a store, it can generally be assumed that they have access to all equipment and items of their tier, as they move from better to better and better stores as they advance through the game. Alternately, previous merchants may simply be acquiring better stock parallel to or as a consequence of the adventure. All of these things can be bought for the listed price.
If someone wishes to sell an item back to the store, it will typically be bought for half its market value. This allows the party to clear old equipment out from its inventory.
One could imagine campaigns which somewhat limit shopping lists - for example, a campaign might exist where only some accessories are available in a given store, on a list provided to the players. Be cautious - the basics should probably never be limited.
Some stores might have relics available for purchase - a mysterious merchant may be offering a once-in-a-lifetime deal for the Zodiac Spear, or a village of dwarves founded over a mythril vein might have rare and powerful mythril weaponry. These are typically fairly overpriced, costing perhaps 30% more than a base item of that tier.
Adventurers get the shaft again - if a relic, found or bought, is for some reason sold to a store, it only garners a price as if it were the basic item.