There is no rule for the exact location of the handles on the doors. We normally come 50mm down then 50mm across to the top of the handle. If the door has a routed profile then we normally line up the handle with the top (or bottom) of the profile. Mark your hole locations in the correct location.
The floor cabinets have the handles towards the top, the overhead cabinets have them towards the bottom, and pantry doors normally have the handles set at a height that is comfortable when you reach out to open it. We normally place our handles vertically on doors and horizontally on drawers.
Once you have marked the hole locations you may wish to use a hole punch and make a small indent. This will help prevent your drill from slipping.
Most handles require a 5mm drill bit to suit the screws they come with, but it pays to check first. If you are not sure you should drill into a piece of scrap board to check for a nice fit before drilling your doors.
Make sure you are drilling into the correct side of the door! You would be surprised how many people have drilled holes in the same side the door is hinged. Hold your drill as straight as possible when drilling. Drill into the face of the door as the drill bit may break out a bit when it comes out the other side. Screw your handles in place and you are done!