Jeans are the bedrock of most casual dress these days - and are increasingly even being seen in the office. They originated as work wear for the likes of miners and were designed primarily for function and durability, but today are far more likely to be seen hanging off the waist of some hipster dude in a bar or a 9-5 kind of guy out washing his car. No surprise then that the jeans buyer is presented with an enormous and dizzing array of choice when out looking for a pair. So what to buy? While the matter of personal taste is subjective there are a few key things to think about when you're buying jeans.
Where will you be wearing them?
If you're planning to buy some jeans for general knocking-around-the-house duties then you should probably factor in price as a critical factor.

Day to day jobs that involve kneeling or coming into contact with mud or water (perhaps gardening) are going to damage your jeans pretty quickly, so it would be daftness itself to spend a fortune. Most supermarket chains carry budget lines, and even high street stores now carry 'own brand' jeans that can be picked up pretty cheap.
If you're buying jeans for something that requires a bit more style or formality then you should pay more attention to the general style of the jeans. Typically, baggy or loose-fitting jeans will look a lot less smart than more fitted styles. Overly long jeans are also likely to drag on the ground, leading to fraying and discolouration so pay attention to length. In general too, darker jeans have a more uniform colour than lighter ones which definitely give them a head start in the smartness stakes.
What will you be wearing them with?
If you're a little bit more involved with matters of style and taste, you've probably got an ensemble in mind to go with your jeans.

A good tip is that brightly coloured tops and t-shirts go better with darker jeans. Belts are the most obvious accessory for jeans at the moment and the current trend is for large belts with decorative features such as studding, elaborate buckles or even printed words and slogans.
Waistlines...
Simon Cowell might be feted the world over for his star-making abilities, but his penchant for wearing high waistlines has made him a fashion laughing stock (proving that money can't buy everything!) Today's style is towards a very low slung waistline indeed - which is why those pesky kids are often walking around displaying their underpants to all and sundry. For most of with normal waistlines, you would actually be better off with a higher waistline to avoid looking like a fool!
Perhaps the single most obvious point - but one we men often fail to do - is TRY BEFORE BUY. If they don't look good in the mirror, they won't look good anywhere else. And if they do look good to you, there's no harm in a second opinion!