I need beef lessons - how do you pick good meat ? Thus far i've winged it on marbling,1.5cm thick, grass fed if there is any.

I stocked up on a kilo of flank because that's all the market had left last week, but my brother said it may not be as tasty. They all look the same to me lol

And how are you marinating / cooking this ? I just use butter, salt and pepper and fry 2-3 mins each side.