Question for military people: If the military wanted to capture a town which was held by enemy forces, how would they go about doing it?

Define "town."

If it's a large city, what's the objective of holding it? If it's a few houses or a village, what's the objective of holding it?

Nowadays, holding urban terrain isn't very helpful and it's expensive to take cities because you get a lot of guys killed in that environment.

I would surround the town or cover the major avenues of approach. I'd offer a surrender and not kill anyone if they gave up their weapons and soldiers. If not, I would plan an attack based on the cover and concealment, the terrain features, and enter at the least-defensible positions available, going after soldiers, armed citivilians, and males of military age.

They sneak up on it and then wack it.

depends on the intelligence they have and what they come up against, every situation is treated differently

Too many variables. That question makes as much sense as asking the question "How do you make a group of people something to eat?".

If there are no non-combatants, bomb it until it is flat, then shoot anything that moves.

Surround it.