Always dry fit your joints prior to solvent cementing. I can’t tell you how many times I had to cut out my freshly glued joints because something further down the line didn’t properly fit.
Not all leaks happen immediately after cementing a joint. Check on all joints immediately after pressurizing, 10 minutes, 30 minutes, 1 hour, 4 hours and the next day to ensure the joint has properly seated and sealed.
If working on a water line and the shut off valve is out of sight, always work in pairs. Phone your partner before you turn the water back on in the case one of your joints did not properly seal. That way you can stop any flooding before too much damage can be caused.
The number 1 tip in plumbing is if you are not 100% confident in the problem AND the solution, hire a licensed professional to do the job for you. Do not risk flooding your house, or causing a long term problem that may not immediately present itself.