Really depends on what you're wanting to do with the model, and how high poly you want it. Modelling legs right to the groin could be a pretty pointless excerise and a waste of polys if you're modelling for a game for example, but only if in the game you're not going to see 'under' the skirt.

In answer to your original question, there is no exactly 'correct' workflow. Across 10 modellers you might find they all tackle a problem differently, but get equally good / bad results. You really just have to see what you prefer doing. You'll settle into it once you've practiced enough.