Check out if you have a dip in you back and how pronounced that is. If you do you are typically an hour glass or pear shape. You need to make the waist band fit, to avoid muffin top due to buying the trouser pant too tight so it doesn't fall down. Same for jeans. Make sure the rise suits and there is a curve on the waistband. If you happen to be more of a boy shape (straight up and down) then a lower rise will work well. It would be fair to say that apple shapes have a hard time when it comes to trousers and I can give not real comfort except to say that a jersey flare with a fold down wide waistband is probably the best option. Such a style is hard to find although they were all the rage many years ago, but the harem is the obvious solution now with this waistband element and the detail of drape.
When you select a trousers do so on the fit around the backside, front, hips and thighs. Any bagging on bum or at the front is a no no as is tightness on the thigh creating creases or bunching. But don't forget you can get them altered. The waist and leg length is easiest and it is easier to take in than let out. If you haven't got a dressmaker use a local tailor, no one is going to turn away custom these days.
Sexy black trousers - probably the best high street retailer for that Helmut Newton-esque model posing in black trousers/pants is Karen Millen. They always have a black pant offering every season and they wash well and hold their shape. A classic cut, they will work for years regardless of the trends that come and go. The wonderful wide waistband should make these work for all body shapes.
Tailored black trousers £120Cigarette Pants - again are a useful must have in the wardrobe. Often with a turn up the essence of the cigarette pant is the fact it is straight and fitted. The forerunner of the drainpipe, the skinny, and the base for designing the peg. It is obvious a straight pencil cut creates opportunity to change the basic template and add to. Whilst a flare is the equivalent of the a-line skirt and as it's strength comes from the cut at the waist. Lots of options from designers such as Rag and Bone to on the high st. Zara have a pair in red currently if you fancy.

Rag and Bone Wool mix trouser £260.00 at Matches
The sexy flare and the cigarette pant are your investment purchases. Spend your money here as quality is a key ingredient to carry off such garments.
Jean territory is the nightmare of most women. I have to say if they don't work for you and the idea of finding a pair is hell then don't bother. They are not what defines you. I do wear jeans but occasionally not everyday and I have only two pairs a skinny and a flare.
The skinny jean - a wardrobe staple and easy to buy anywhere. Topshop's Baxters are a firm favourite but I always have to have the waistband altered as I need the right fit on the leg which leaves a gape at the back but an inverted triangle reduction always resolves it. If you've got wide calves then the straight jean will be a better option.
The flared jean - this is a personal favourite so I'm not particularly objective about it's value because I love a flared jean. I prefer the skinny flare to a true flare but that's a personal decision and always go with the proportions of leg that suits you. The Made in Heaven brand do a wonderful retro pair and again only buy at this price if it is the look for you. You could have 10 pairs of jeans alone and there is no reason not to.

MIH retro look jeans £148 Matches.com
The flared jean always reminds me of the Charlie! Revlon advertising, an inspiring image for a stylist.

Leather trousers(!) - the rock look only please. I'm thinking men and women who've pulled it off. It needs boots not high heels and a good t-shirt. And for goodness sake never wear a leather jacket on top as well think Jim Morrison not the Fonz. I know Balmain have worked that leather pant with statement heel look but I still think it only works with a good tee. It needs that dress down rock chic element to really work. Mind you Hermes worked a great leather look reminiscent of the Avengers for A/W 10, so in reality there are no rules...just advice that morphs.

A colourful cotton pair - you now what I mean, it's like a jean but not. In red or any bright bold colour it adds zing. Find them in Uniqlo, Gap or Zara. A grey t-shirt is a fab look with a coloured jean trouser.
A chino - the chino has had a come back and whilst I can't grab an image from the Oasis website, I've linked it. The point with a chino trouser is, it is very much at the whim of fashion trends, and I would say go cheap and cheerful but on trend rather than see it as an investment buy.
The jodhpur - who can forget the influential Balenciaga A/W 07 collection when you all sported a J Crew blazer in lieu of getting your hands in the real thing. Well the real star of the collection was the jodhpur trouser and it is still around, next season it will be in black. Again given the trend nature of this item, head to H&M or COS for a reasonably priced and designed pair. Or find a genuine pair at a car boot or charity shop and dye them.

Shorts - A city short works all year round with the added help of thick opaque tights. The staying power of the short is assured with new designs and materials - this season it is all about the leather. Try a few on to get the right cut and length for your body.
The Jumpsuit - I know there is nothing worse than a convert but if you need a wow factor and you are more of a trouser kind of gal then you need to jump to it. ASOS is awash with jumpsuit that don't cost the earth.
ASOS Assymetric Shoulder Jumpsuit £30I feel I've left out the sailor trouser but again adapt your top ten to suit your preferences and if you add it on to make 11 then I won't tell.