To keep a twist drill from skating on metal (and leaving you with a hole in the wrong place) you should always use a center punch, especially when using small flexible bits. The dimple created by the punch holds the bit point true.
The Veritas optical centre punch simplifies the procedure at the same time as it substantially increases accuracy. Even with wood there is an advantage to using a center punch; it creates a small crater that readily centers a brad-point drill.
After you have carefully marked your spot, place the punch base and optical post over the spot, adjust it until the crosshairs on the 8X magnifying post are exactly on the mark, then replace the post with the A2 hardened steel punch and tap the punch with a hammer. A high-friction O-ring in the gold-plated brass base keeps it from moving during this exchange, ensuring near-perfect accuracy. It is simplicity itself to use.
As an added bonus, you can use the 8-power optical post as an inspection monocular in your shop. It has excellent depth of field and is easily focused freehand.