This guide relates to sizing FEMALE jeans/slacks/trousers and how to get the best fit for your particular body type.  There are several key points to remember, which are listed below, while the lower half of the document deals specifically with concealing or accomidating the most common body "flaws" for females buying jeans.

-Measurements range between STYLES within a manufacturer and from manufacturer to manufacturer, so knowing your general size isn't enough.  Buying online, it's impossible to know what size product you will receive unless the seller lists the measurements for the garment.  Never buy items that fail to list their actual sizing specifications.  Remember, there's a reason for every product auction.

-The waist/hip measurement is generally your widest hip measurement, though it can be lower.  How much of your hips are exposed depends on the pant rise.  Generally, a 7-8 inch rise is just below or above the pubic line and is the lowest rise manufactured.  The average rise is 9-10 inches and lands just below the belly button.

To see how a particular rise will fit YOU, center a tape measurer at the middle of your crotch and lift until the rise reaches the desired in/cm measurement.  You may then take what the seller calls the "waist" measurement from here.

To see how a particular waist/hip measurement will fit you, measure around at the widest part of your hips.  Unless you want your clothing skin tight, add 2 inches to your actual measurement.  For a baggy fit, add 3-5 inches.

-The inseam/leg measurement this is the length down the leg from the crotch to hem.  Average length is 32-34", while short is 29"-31" and long is 35"-37"; again, always check the measurement.  Nothing's worse than high water/flood pants!

-The thigh measurement this isn't generally listed, and usually, the hip measurement will suffice, but for "skinny fit" jeans, it's very helpful.  It is the measurement around the smallest portion of the thigh of the jeans.  You should measure the LARGEST portion of your thigh and add 2 inches or 3-5 inches.

Problem Areas/Fitting with your jeans:
The flat butt
Stay away from baggy clothes!  Purchase pants that fit the waist with a high inseam.  This cut will support what you DO have, accentuating its shape and making it more prominent.  Straight-legged pants also draw attention from your rear by aligning your legs proportionately with your hips, waist and butt.

The big butt
Stay away from baggy clothes!  For those of us, (myself included), with a butt that rises near the top (like a ledge), I reccomend boot cut styles, with distractions like carpenter, worker jeans, and cargo pants.  These provide a smooth vertical line and silhouette, while drawing peoples' eyes to the pockets, instead of your flaws. 

-Avoid high-waisted pants; the extra height makes your rear look extra long.  This means, you want to go with a SHORT rise.
-Avoid pleated pants, which highlight the hips; flat-front trousers slim your thighs and trunk.  Invest in a ¾-length jacket to make your bubble butt disappear.

The short-waist is a much-desired female condition where the legs are longer than the torso.  The thing to remember is to measure your inseam and choose LONG length jeans/slacks/trousers. 
If you want to make your legs seem shorter:
-Hang your pants from your hips, not your waist.
-Wear pullovers/sweaters instead of button down shirts; this will help disguise the length of your legs.
-If you MUST tuck in, match your shirt and belt colors, but not tucking in is generally advised for your body type.
-Best pant cuts:  slight low rise, flared bottoms,

The long-waist is a common problem where the torso is long, and the legs are short.  Some ways to combat this problem:
-Stand straight.  Good posture always improves the look of your clothing, but it is especially prudent for long-waisted individuals.  Additionally, a corset or shaper may help streamline your figure and hide the start of your hips.
-Wear a top that contrasts the color of your pants. This breaks up the vertical line of your body.
-Wear your pants at or around your waist, not on your hips.  If you want to wear on your hips, wear a style that is fitted down the thigh and flares at the knee. 
-Always tuck in your shirts.
-Don the punk-style and wear suspenders or bondage straps, which create the illusion of a higher waistline.
-A large buckle belt will draw attention to your legs and make them look longer.
-Pleated slacks or uncuffed slacks will also make your legs appear longer.

The big tummy is a problem that almost every woman faces at some point, due to aging, pregnancy, or other factors of her lifestyle.  To camoflauge this:
-Wear light fabrics.  Avoid all heavy fabrics; these include tweed and flannel, opting instead for natural, light fabrics (such as cotton) in dark hues.
-Single color pants, (black, brown, navy), will help disguise the size of your stomach.
-Trade horizontal pinstripes for vertical ones, which provide a slimming look.  Pair up stripes (pink, grey, blue, or red work wonderfully) against a dark background.
-Ban T-shirts from your wardrobe.  Loose, these make you look bigger, while tighter T-shirts emphasize your stomach.  They look even worse tucked into your jeans!
-Pants should sit just at your belly button.  Wearing them lower will accentuate your problem area, while wearing them higher will accentutate your rear.

Big thighs are a common limitation of our female genetics.  To disguise these:
-Wear colorful shirts and blouses with your pants.
-Avoid brightly-colored pants or hip huggers that will draw attention to your lower body.
-Avoid baggy pants!  You want your clothing to look fitted but not tight.

Big hips are ANOTHER common limitation of our female genetics.  To disguise these:
-Avoid any jeans/pants/slacks/trousers with zippers on the side, which only draws the human eye to the distraction and your hips!
-Light or bright colored pants.  Pair dark pants with a light shirt to accentuate your bust.
-Skirts with pleats.  These little babies tend to flare around your thighs, drawing a boxy line up to your hips and making them look wider.
-Avoid baggy pants!  Have you noticed a trend?  -Small or large-framed, baggy pants always make your perfect outfit look sloppy and accentuate your natural flaws.