Brush up on your airline's policies
One of the best things you can do before you fly is familiarise yourself with your booked airline's policies. Know what their contract of carriage is, as it will outline how an airline handles various scenarios, such as delays, missed flights, and more.
Consider other transportation options
If your airline won't re book you without a pricey penalty, it may be time to consider other options. Sometimes, it's less expensive to buy a brand new ticket from other airlines, fly out of a neighbouring airport, or to re-organise your agenda to fly out on a different day. If your flight was scheduled to be short, you might be able to get to your destination faster with a ground transportation option like a rental car, bus, or train.
Adjust your agenda and/or accommodations
Missing your flight will likely have an impact on your itinerary, whether you're traveling for work or for fun. Consider things like airport pickup and transfers, along with your scheduled accommodations. Be sure to let a hotel know as soon as soon as it's clear that you won't be on time for your reservation, especially if you need to cancel it entirely. Your goal here is to avoid extra charges made to your booking.
Look into compensation
If you missed a connecting flight because your first flight was disrupted, you might be eligible for compensation from your airline.
Talk with airline representatives
Before you start to stress out, talk with airline representatives about your missed flight. Explaining why you missed your flight is the first step. Some airlines have an informal 'flat tire' rule which means they can book you on the next available flight, should space allow, if you missed your flight for a good reason.