If you’ve never done it before I would suggest getting a hand from someone who is experienced and not a bodger.
Only problems I have are on cars that are not mine or new to me as previous owners/’mechanics’ have not done things right or they have been neglected.
Common problems/mistakes:
Getting the large caliper/yoke bolts undone as they can be very tight and seized.
Disc bolts are often seized due to lack of copper slip and might have mangled heads or most likely have the heads snapped off so you cant install new ones. Not a huge problem as all they do is hold the discs in place when the wheel is off but you want to try to avoid spining the disc on the with the wheel off as it might not sit the same due to any run out or corrosion on the hub/disc so try to keep it in the same position when doing any work.
Caliper sliders are often sticky and gunked up – strip em down, clean em out with brake cleaner and relube with brake grease (not copper slip). Also check them for wear and play and replace if needed.
Pushing or winding in the piston can be tricky (make sure you know if it’s a winder or a pusher to retract). May need special tools, but can often be done without in some way
Get a set of wire and plastic brushes and a file to clean up all the sliding surfaces and retaining pins (plastic brush near any seals/rubbers so you don’t damage them). I am amazed by how many people just throw brakes back together without cleaning all the caked up dust and rust and relubing.
Make sure you have all the anti-rattle springs and retaining pins etc. It is not uncommon for them to be missing either due to being fitted wrong or lost and not replaced. They are normally quite cheap to replace and make sure you know exactly how they fit.
sometimes you have to replace the mounting bolts after a single use. They will often come with the pads if that is the case. Use threadlock on the retaining bolts (you will see the left over threadlock if used on the thread). Clean the old stuff off with a wire brush or it jams up the threads and makes refitting the bolt a lot harder.
Pick up a tube of brake grease (Mintex ceratec or the pagid version for example) when you get the new pads.