If you only have one full day, resist the urge to cross Montreal six times. The strongest day gives you historic Montreal, the mountain view and one taste of neighbourhood life.
Morning: Old Montreal
Start around Place d’Armes and Notre-Dame Basilica, then walk toward the waterfront. If you enter a museum or the basilica, accept that you will see fewer streets.
Lunch: stay central
Eat in or near Old Montreal rather than burning an hour travelling for a famous lunch.
Afternoon: Mount Royal
Make the Kondiaronk lookout your priority and give yourself enough time to enjoy the park.
Evening: choose one neighbourhood
Finish in the Plateau or Mile End. Do not try to do both deeply.