The perfect dress is all about the details

I am a 20-year-old fashion student and I want to make my sister a dress for her 25th birthday. Can you suggest how to make it stand out and last?
Julian, by email

Would that we all had such a brother, Julian! Little siblings of all stripes out there, can you hear me? Whatever advice I give in this column, it pales into invisibility next to the life cues you should be taking from Julian here. On behalf of older siblings everywhere allow me to say, younger brothers and sisters: this is how it's done.

You say you want the dress to last, meaning, I suspect, that you are not asking what this season's trends are, and quite rightly not. I suspect what you really want to know is what little details you should add to make the dress feel properly special and, on this issue, you have come to the right woman, Julian. I can't even thread a needle but I am a connoisseur of (French for "sucker for") special details on dresses.

The first thing I would say is, be very careful with the length. About 80% of the dresses on the high street are unwearably short and I think this might be because manufacturers forget that women have bottoms which require extra fabric, hence the phenomenon of a dress being of a modest length in the front but decidedly less so in the back. So don't judge the length of the dress by holding it up on your body, Julian. Men's bottoms tend to be flatter than women's and you will get a wrong idea of the length. Borrow a woman (another sister? Your mother?) and measure it on her to spare your birthday sister years of awkwardly tugging down her inadvertently pornographic dress.

Next, pockets. I have yet to meet a woman who doesn't adore a dress with pockets. Pockets are doubtless old hat to you but to women they are the hen's teeth of clothing detail. With the exception of jeans, women's clothing is largely frustratingly pocket-free, mainly out of manufacturer laziness but also because designers think that women fear added bulk on their frame to such an extent that they would abhor a pocket. But this, in my extensive experience of being a woman and wearing women's clothes and hanging out with other women who wear women's clothes, is to overestimate how much the majority of women care about bulkiness over convenience. Personally, I prefer pockets that sit on top of the fabric as opposed to ones that go inwards, simply because the latter often get bunchy and look a little messy, but I leave that decision up to your fashion scholar's taste.

Let's talk buttons. Buttons are great. I've been known to buy dresses I don't even like that much simply because they had amazing buttons, and that's a key thing here – the buttons need to be amazing. The prettiest are covered buttons, ie individually wrapped in the same fabric as the dress. This is obviously more expensive than your common or garden plastic buttons, but even just three little wrapped buttons at the top of the dress on the front or back, or one each to cinch the cuffs, will make the dress look, as the poshos say, a cut above. Think back to Pippa Middleton's bridesmaid dress at the royal wedding: while those of a lesser mindset were all drooling over Pippa's Sloaney backside, we fashion connoisseurs were busy drooling over the cascade of covered buttons down the back of her Alexander McQueen dress. Bottom v buttons: I know which I care about more.

Finally, sleeves. Your dress needs sleeves if you want it to last – spaghetti straps are tatty and annoying and render the dress useless for 11 months of the year in England – but make them of a proper length. Cap sleeves are uncomfortable, sweaty and unflattering on anyone who has arms thicker than matchsticks and I personally cannot stand those stupid bracelet sleeves that end three-quarters of the way down your arm. So if you're going for long sleeves, make sure they end at the wrist, and short sleeves should end just above the elbow. Finally, to make the sleeves special, make them in a contrast colour to the rest of the dress. I adore colourful dresses that have black sleeves – Roksanda Ilincic and Victoria by Victoria Beckham, two labels that I think make some of the best dresses around these days, both do this, and it makes the dress both look and feel so elegant.

That's it, Julian. As to everyone else, feel free to use any of these tips on dresses you already own or buy in the future (swapping buttons is one of the easiest ways to smarten up cheap high-street buys). I, on the other hand, simply plan to kidnap Julian at some point so he can be my dressmaking brother.

Post your questions to Hadley Freeman, Ask Hadley, The Guardian, Kings Place, 90 York Way, London N1 9GU. Email ask.hadley@guardian.co.uk

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