Ready to Wear: This summer it's anything and everything nautical

Susannah Frankel: The nautical look is, of course, quintessentially French, so it must be chic

The mere thought of summer dressing might be enough to bring about an almighty case of goose pimples just now, but the truly committed fashion-follower is busily investing in what are known as "key pieces" for the new season as I write. Look out, then, for the following:

Zingy colour. Yes, citrus shades are well and truly with us. Those less than enamoured by the concept of dressing like a lemon would do well to pay lip service to the look by introducing it via accessories. Bottega Veneta's woven leather belt in tangerine and Miu Miu's suede pumps in an equally orangey hue are lovely.

Masculine blazers. At Gap, they're cotton drill and look particularly good in khaki. At designer level, the Stella McCartney boyfriend jacket is as slouchy as it is smart.

Anything and everything nautical. Although the maritime trend, as much a part of classic summer dressing as the strappy sandal, was not as prevalent on the catwalks as it has been, there's still plenty to choose from. Burberry's classic Breton sweater, D&G's striped vest, and, at Jigsaw, sailor trousers and more. The look is quintessentially French, of course, so it must be chic – we have Coco Chanel to thank for making it fashionable in the first place.

Complicated trousers. A degree in rocket science is not quite necessary in order to tell the difference between a banana and a carrot trouser, but it might help. The single thing that unites trousers this season is that the more unconventionally flattering they are, the better. Harem, dhoti and gaucho trousers are everywhere, from the catwalk down, and are only recommended for those who don't mind that their bum most certainly will look big – not to mention decidedly droopy – in them.

Jeans. Hmm. The world's most democratic garment is going through what might best be described as a transition period. The truly fashionable will be wearing theirs battered and faded almost to the point of nonexistence, but others might be relieved to know that the 7/8 skinny (that's cropped at the ankle) is also a pretty safe bet (J Brand's are pleasingly logo-free), as indeed is the flare, making something of a comeback (again), and most up-to-date when skintight to the knee (J Brand again, but also Earnest Sewn and James Jeans).

Tailored dresses. Alas, the all-forgiving tunic is no more, and in its place come extremely grown-up figure-hugging designs courtesy of everyone from Alexander McQueen to RM Roland Mouret. Don't try a cheap option here – these dresses don't translate well on a budget.

Failing that, frilly is the future (dear me, well, they do say opposites attract...), as seen pretty in pink at Topshop, but not to be worn by anyone over the age of, say, 21.