This was originally meant to be a part of the 140+step concrete lathe project but it is too important to risk it getting buried. It was taught to me by a guy who has been an expert mechanic for over 70 years.
To start your hole in metal, use a sharp scriber AND SCRIBE THE INTERSECTING LINES JUST ONE TIME. This is very important because it is difficult to re-scribe the line exactly.
Use a thin, very sharp punch (stupid program will not let me type p r i c k punch but that is what it is) to lightly punch the intersection of the lines just one time. You should be able to slide the punch tip along the line and "feel" the line intersection.
Examine the punch mark in a bright light and if necessary "drift" (tilt the punch) the punch mark over (using the fine punch) to get it in exactly the right place.
Use a heavier, sharp punch to re-punch the smaller mark and make a dimple. Be careful here because sometimes a punch mark will work harden the metal and will actually be harder to drill than it should be.
Use a small bit to drill a pilot hole.
You may have to "step" drill with increasingly large bits to keep the hole on center.