Here are the factors I would want to know to answer this question:
- Through what airports are you flying? For airports with multiple terminals, if you are connecting at such airports, from what terminals do your flights arrive and depart?
- On what airline(s) are you flying?
- Is the booking on a single ticket, or on two tickets?
- Do you have checked luggage?
- What nationality are you, if you will be clearing customs and immigration at any of these airports. This can affect the speed of the customs and immigration process.
- Do you hold membership in any trusted traveler or preferred security program, like TSA Pre, NEXUS, Global Entry, etc.?
- Do you have any mobility issues? Are you traveling with any traveling companions that have any mobility issues? Are you traveling with any children? (If so, what age?)
- How unwieldy is your carry-on baggage?
- What time of year will you be traveling? (Weather can increase the risks of delays.)
- the times of flights (airport security sometimes needs to be cleared, and it will depend on time of day as to how long it will take)
As for resources:
- airline websites - generally discuss minimum connection times and the connection logistics at their hub airports. They'll also discuss customs and immigration issues (e.g. international connections, e.g. London to Toronto to Tokyo, or connections involving preclearance/juxtaposed controls, e.g. flights to the US from most larger Canadian airports)
- airport websites - will discuss the connection logistics in more detail and give a sense of the timeframe required, along with customs and immigration concerns. They'll also often discuss whether bags need to be picked up during international transfers. You can also get a sense of what gates a given airline is likely to use, as some connections may involve a walk across a terminal, or even a terminal change (e.g. changing between the main United terminal to the regional jet terminal at Chicago O'Hare may involve taking a bus).
There are so many variables. Domestic-to-domestic connections can sometimes be made in just a few minutes, particularly at smaller airports. On the other hand, connecting at London Heathrow from an international flight could be difficult with a three-hour connection because this summer, some international arrivals have had processing times at UK Border Force of as much as 2 hours and 38 minutes.