I need to alter my trouser pattern and make a muslin before I can even start sewing them, this is a pain to do and is the hardest part of dressmaking in my opinion. It involves cutting your pattern out in a cheap fabric, I generally use bleached calico, fitting it to your shape, making a note of the alterations and transferring the alterations to your pattern. It isn't as easy as that because the practise garment is on and off hundreds of times ( well I may be exaggerating just a little) to get the right fit.......I tend to want to overfit, but 2ins of spare room is needed at the hips for comfort so you can sit down.
You may ask why do I do this, the only answer I can come up with is, lovely comfy clothes, no tight waist squeezing the life out of you and crotch seams nearly cutting you in two.
The only trouble is, if my trousers go horribly wrong I won't want to sew anymore ever again as long as I live, then I wake up the next day and start making mistakes all over again lol lol.