One thing that can be a real pain when re-assembling the trigger group is keeping the trigger assembly together while installing it in the housing. This video shows how to make and use a cheater pin to solve that problem. If you ever bought a trigger upgrade kit, you probably got one in the package, but if not, it’s easy and cheap to make your own.
A refinement that isn’t in the video: Ideally the pin should be just shorter than the width of the trigger. That way when you line everything up and insert your actual trigger pivot pin, it will already be started into the trigger and will stay lined up as it goes in.