Just use an external, incident light meter and, if you want, overexpose by some sensible amount (1/2 or 1 EV) and you'll hit anytime.

If you use reflective metering, the metering will vary according to the reflectivity of your subject (bright or dark). If you take a picture of a dark subject (skin, hair, dress, background, whatever) your reflective metering will tend toward overexposure. If you then further overexpose, you end up overexposing too much and you'll have a "miss".

Incident light metering will not be influenced by the characteristics of the subject and will give you the same reading whether the subject is bright or dark.

If there is one field of photography where incident metering wins hands down over reflective metering, I suppose that's portrait.

Fabrizio