Rams and catapults
Rams hit the wall. Catapults hit a building you pick — or a random one. Both are workshop units and both are slow. On a windowed server that slowness is a plan, not a nuisance.
Rams
The wall’s defence bonus dies with the wall. City Wall (Romans) is the toughest, then Palisade, then Earth Wall. A conquest wave that leaves the wall up is wasting chiefs.
Catapults
This world shows catapult targets in the send UI. Aim the Palace or Residence first if you want the village. Aim resource fields if you want to starve it. If population hits 0 the village is destroyed, not conquered. Gray tile. No owner change. Do not do that on a village you wanted.
Several buildings of one type
Stock Travian
Catapults hit the highest-level building of the type you chose. A random target ignores that and can land on any level.
Travikas
Every standing building of that type is an equal target. A level-20 warehouse is as likely as a level-1 one. The chance depends only on how many of that type are still standing.
Three warehouses means each one has a one-in-three chance. A warehouse already at level 0 is skipped. If none of that type are still standing, the shot goes to a random building or field that is. Great Warehouse is a separate target, so a Warehouse shot leaves it alone. The same rule covers granaries, cropland, and every other type you can aim.
Rally Point 20 and at least 20 catapults open a second target. Each wave picks on its own, and the damage is split in half. The first wave lands before the second pick, so a warehouse knocked to 0 drops out of the next roll. A damaged one can be chosen again, including the same warehouse twice. Leave the second target empty when you want the full hit on a single roll.
Travel
Workshop units walk at 3–4 fields/hour before troop speed. At 10x that is still a long walk across a 25×25. Send them in the evening to land in the morning, or accept that a siege is a two-session project. Use the travel calculator.