There are a lot of variables. A few are:
The kind of rock and the conditions it is exposed to.
The purpose of the bolts, i.e. belay/rappel/top-rope anchors or lead protection
The means of placement, i.e. drill by hand or use of power tool
Are these bolts new placements or replacements of old mank?
Of course there are the personal choices too, such as if you are bolting a new route will you start from the bottom and go up, or place your bolts on rappel?
These things and more will influence what kind of bolts and tools you will use, and what sorts of knowledge, experience and skills you will need.
FatDads question is valid too. And as Michael said, apprenticing on an ASCA rebolting project can be good experience for learning how to remove old hardware, clean up the mess and place new modern bolts. Lotsa hard work…
Basically though, if you are the type who’s good at building stuff and fixing cars, placing safe bolts should not be very hard to figure out. The common newbie mistakes are:
Choosing the wrong bolt for the job.
Drilling a tight hole. In granite the hole should be very slightly tapered at the mouth of the hole. This is done with a power drill by slowly wobbling the drill a little bit for the first part of the hole, same with a hand drill but it’s slower. Otherwise you will have to hammer too hard on the bolt while driving it in which work hardens the metal weakening the bolt. I’ve new 3/8 bolts fail due to this. Worn out bits will make a tight hole as well.
Over tightening the head or nut. Another nice way to weaken an otherwise good placement.