I once heard, that with dating, you have to "heat the oven up" before you "put the turkey in"?

The are a couple of schools of thought here. On the one hand, being true to yourself always make you more authentic. On the other hand, you want to give yourself the best chance to stand out. It very much depends on the kind of girl that you're shooting for, but for some very pretty girls it's a little redundant to tell them that they're beautiful in the early stages. They probably already know that and even if they don't they've still likely been told a thousand times. There is also the danger that you set yourself up as being beneath them, in terms of elevating them to a high status before you even know them. That can appear unattractive.

It's probably better to reserve the higher compliments until they have been earned and will seem more substantial and meaningful. Telling her that she's beautiful when you really know her will carry more weight.