There are several trends leading up to the warmer season, but I would position denim first. Jeans and denim jackets are a must, of course, but this is a tidal wave of denim accessories, such as shoes, backpacks, and bags, which doesn't seem excessive now, but ...
Stars are fashion designers' top choice, which they've already hinted at last year, and by now they're a fun addition to every piece, especially jeans (all over in Stella McCartney's version) and shirts (country style is a big trend).
The way to find your perfect denim jacket is by first deciding on a colour. A lighter one is more appropriate for the warm season, and dark for the winter; I would definitely advise against going too dark, because it will be more difficult to style.