considering what a crazy trip this has been with learning how to make a jeans pattern i thought i'd go over what i've taken away from this experience.
do lots of research. especially with pants. of all the garments, it seems as though pants are the trickiest with perfecting the fit. there's tons of stuff online with questions, suggestions, and answers. i bought most of the fitting books along the way. i should have done this beforehand; in fact some arrived after i had already drafted the final pattern. none of the books i got were perfect, but each one taught me a little bit more, and in slightly a different way than the other one helping me to better understand what was going on.
you're going to go through a lot of test slopers and fittings. this is highly annoying, but essential to the process of getting just the right fit. there were 21 slopers i had been saving in a box since i started this whole thing, and most of them were altered at least once. granted the black and white ones in the upper left were for the bad (early) pattern, and the red ones were a test pair idea that i scrapped, but still.
get yourself a nice big roll of brown paper. as with the test slopers above, aside from minor adjustments, you're gonna need to draft a new pattern. i was lucky enough to find 2 huge rolls of thick brown paper that a matza bakery in my neighborhood was throwing out right before i started doing this. score!
whenever i drafted a new pattern i never just traced the old one. i drew up this original master sloper pattern and for each new alteration and test i would put a new piece of paper under this one and punch a hole with an awl at all important points--hip line, waist line, center line, crotch line, and along any curves etc. for each alteration that i did that worked the way i wanted it to i added it in a different color onto the master pattern. this helped in understanding what i was doing and how it related to the original pattern. the other thing was that each time i would have traced the pattern would have added a fraction of an inch to the overall size (granted, the size of a pencil line), but after 10 redraws that could have potentially been a 1/16 or 1/8 of an inch. the seemingly minor differences in pattern widths and angles is crazy, but something that really got me to understand it is that if you're only off by an 1/8 of an inch on each of you're seams (say, at the waist) that's a total of 1 inch that your final garment will be off once it's all put together
crotch length. i think this was the biggest thing i learned. no matter what you do to the pattern, how you alter it, how much you scoop out the ass, or how many little tweaks you make to it the crotch length has to remain the same. if you remove an inch from one point, you have to add it back in somewhere else. it helped me to think of it as that measurement actually being my body. that length is my body and my body ain't changing (trust me i've tried). the only way the total crotch length should ever be changed is when an equal amount is increased or decreased to both the front and back--this only changes the rise of the pants, otherwise, make sure it's the same.
use the jeans you already have as reference. you bought them because you liked them so there's things you can learn from them. figuring out how much ease you like around the hips or thighs, how high you like the rise of your jeans, the pocket openings, pocket placement, all of this can be shorthanded by just looking through your closet. it's also good because you can go through and pick apart the things you don't like about those garments and change them for your custom pattern.
once you're on your final draft wear them around for a couple hours. of course i didn't read this until after i was cutting into my nice denim, but after i read that i was like "duh". you're not designing a unmovable column of fabric, and although you may be perfectly still for the fittings, in everyday life you're going to be moving around a lot and you'll notice how things fit differently and settle in.
and finally, (at least in my case) learn to love your wrinkles. (i should be a beauty editor, right?) maybe on some perfect model body with an amazing ass you could design some tight denim jeans that would fit perfectly and never wrinkle under the butt, but not on mine. i think i did a pretty good job of fitting my jeans with what i was given. i know now that if i didn't have those wrinkles i'd be flashing everyone my ass every time i bent over.