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There's nothing wrong with the way you're doing it. As you gain experience, you'll be better able to anticipate what power level of your flash will be needed. Lots of really good photographers do it that way. You didn't mention it in your post, but a bit of thought about the ambient is also important, because it establishes the basis of your entire photo. Slightly underexposing the ambient, for example, enables you to make your flash-lit subject more dominant in the image. Overexposing with just a bit of fill on the shadow side is also a perfectly viable strategy. Either way, dialing in your flash "to taste" is often more easily done by chimping than by using a meter, unless you want to be really precise.