Each chapter has a few key 'point of no return' moments:
In Chapter 1, as you noted, Of Monsters and Men is your final quest.
Chapter 2 ends with the opening of the Mysterious Tower/the placing of the ten stones in the monoliths. However, the key moment you'll want to delay to avoid closing out sidequests is completing the autopsy - doing it too soon can lock out some other investigative paths for Vizima Confidential and related sidequests.
The easiest way to avoid finishing Chapter 3 too early is to simply delay attending the Posh Reception at the New Narakort. You can finish the vast majority of side quests before attending - all that's left afterwards is either Primary Quests, turn-ins to NPC's who were at the reception, and a single sidequest which is completed by running through the main quest after doing some earlier footwork.
Chapter 4 is a bit cleaner; the two main quests that must be completed to advance are Ripples and The Heat of the Day - once those two are finished, the landscape will shift dramatically and you'll have trouble completing further sidequests.
And finally, Chapter 5 is extremely linear - the final quest, Sweet Revenge is nearly impossible to encounter without having passed through the rest of the chapter and done whatever else is there to be done.