All the rules that apply for well dressed boys apply for girls too - and often look even more awesome. Girls in boys clothing trumps everything else. A.P.C usually do it best. You can get A.P.C from Fabric in high street - they have some great A.P.C jeans at the moment actually, if you like your denim super raw. Also, it really is time to start thinking about Autumn clothing.
All boys should own a really good ribbed sweater - I tend to prefer grey, charcoal or navy. Likewise they should own pinstripe trousers. Putting these two linear garments together looks really good, as you can see here. As does the classic snug-scarf-wrap.
Coats are severely underestimated and under-purchased by young men. Which is a shame because they tend to make you look infinitely better. And have the added bonus of making whatever is underneath - be it jeans and a sweatshirt or trousers and an oxford - look three times as cool. This brown herringbone coat with a hidden placket is simple and classic - and short enough to not be too overwhelming or intense.
So that coat, it's here in this look too - this time in a fantastic charcoal check. You should probably buy both of these coats. That tonal charcoal thing is also in this look, with the coat worked back against a great striped sweater and some good trousers. So easy - three good pieces (four if counting a tshirt underneath) and that's all you need to look cool and classic.