Your exposure should be governed by knowledge of the film's dynamic range (in particular reversal film); once you have established that, then the meter will guide the way. This is the major problem where photographers do not become clued up about the film they are using, relying instead on what the meter is telling them and the film delivering an unexpected result. There is room to experiment, increase and reduce exposure but as I said before this is dependent on experience of how the film is reacting to your metering: it's a completely different (and I might add, much more reliable) affair than in-camera meters, that's the fun part: essentially we are smarter, but we still have to learn to be smart!
Thanks for the reminder. I'll have to waste some to get the knowledge, but it should be worth the loss.