Choose one resource type
Choose wood, brick, wool, grain or ore. Opponents transfer all cards of that type to you. Their buildings and development cards are unaffected, and the effect does not take resource cards from the bank.
Because cards come from opponents, an empty bank does not stop the effect. Conversely, a full bank can be a sign that relatively few copies are circulating in hands. Your own cards also matter when interpreting that public supply.
Watch production and spending
Recent public payouts tell you which resources entered play. Buildings and bank exchanges reveal some cards leaving hands. A player who received ore and then built a city probably has less of that ore left than their earlier payout alone suggests.
Private thefts and incomplete information prevent exact hand reconstruction. You can make a useful estimate from the visible board, bank and events without pretending to know every opponent’s current cards. Recheck after new actions rather than relying on an old count.
Collect cards you can use
The largest possible haul is not always the best. Six wool can be awkward if you need ore and have no favourable wool port. A smaller ore collection may directly complete a city or support a development-card plan.
Before choosing, describe the actions the expected cards unlock. Include legal building locations and your remaining pieces. A large hand without a useful spending route can leave you exposed to the next seven.
Wait for the right turn, not an imaginary perfect one
Monopoly is an action development card: a fresh purchase must wait until a later turn, and you can play only one such card per turn. It can be used before rolling or during the ordinary action phase when eligible.
If your roll has just paid several opponents the resource you need, the action phase can be a strong moment. Waiting another round may improve the haul, but it may also give everyone time to spend it. Compare those real alternatives.