"Settlement Besieged" -- what do you do?

[Prodigal]

That's not a single answer question. If heavily outnumbered & have no relief force available sit & wait to defend. If the numbers are against me but I have a decent force & there's no relief, sally & do as much damage as possible with as little loss as possible, this has two results, you either get them to run, or at least do them some damage too. If I'm even close to their numbers, chase & destroy their army, then head straight for their nearest city; this has two benefits, you get you're own back & the follow up stacks they've probably got coming towards you, are fought on their land rather than yours.

[dismal]

I almost always sally out immediately.

This is because I almost alwasy garrison at least 4-5 archers and a couple spears in a border city, and can use this army to beat (or at least inflict pretty severe damage on in a "draw") most of what the AI brings.

If I don't have enough defenders (in relation to the attackers) I'll try to get a relief force there. I'll try to position them on the opposite side of the city from the besiegers, which allows me to get them inside the walls and then use my sally out tactics.

Actually defending a siege I almost never do, and if I do it's usually because I was so undermanned I couldn't sally out so it's an inevitable defeat.