Tips on 80% lowers:
This is what I found, YMMV
Have an upper on hand before you start
Have a lower kit on hand before you start.
Several of the hole sizes on the print are unclear/incorrect. Having the parts on hand allows you to double check before you drill.
Have several mags on hand to size the magwell. If you plan to use thermolds or orlites, use one of those.
If you have to open the bolt catch slot, move it toward the magwell, not the trigger.
Use reamers if you can get them, an adjustable reamer works great on the safety hole.
Buy a NEW set of drills before you start.
Have a file card and use it, the alum chips really clog a file.
Take your time, measure twice, cut once.
Edit to add:
Plan to drill the counter sink for the rear takedown pin before you drill the hole, otherwise you will need a piloted spot facer. A "bullet bit" works well here.
To drill the bolt stop roll pin hole: measure and center punch (with auto-centerpunch) the hole location from the rear. Start hole with small dremmel ball cutter. Now you can hand drill it with a 12" bit, very easy, no jig or press needed.
Also, use oil on every hole you drill, will keep the bit cleaner and the holes will be more accurate.