Where to shorten may vary for your figure, but these are the most common locations to shorten or lengthen a pattern:
BODICE: below the bust in the midriff (tummy) area.
LONG SLEEVE: either or both above or below the elbow, depending on where your elbow is. If the pattern does not have an elbow dart, then pick any place close to the middle.
PANTS: at the crotch, and either or both above and below the knee, or in the middle depending on the pant style.
SKIRTS: any place below the hip
This tutorial deals specifically with how to shorten a bodice pattern using the Tia Dress, #LN1312, but the same methods and rules apply for shortening the length of a pattern in any and all locations, standard or not.
Now you might ask- what is a backwaist??? The backwaist is a sewing term used to mean the measurement of the space from the neck to your waist. You'll be looking for that prominent vertebra at the base of your neck that sticks out just a little more than the others. Your waist is an anatomical space between your rib cage and pelvic bones where your body bends in half to pick something up. Yeah, we'd like to think it's the smallest part of our torso or we could pretend it's three fingers above the belly button, but that doesn't make it truth! If you have a hard time finding these two places, put on a chain necklace that has some weight to the front and a tightly cinched narrow belt. Feel around for that gap between those bones, and it may help to bend around a bit to check that the belt is settled into the right spot. Measure to the bottom of the belt. It's better to be too long than too short!
Now, if you'll turn to page 6 in your instruction booklet and work along with me, here is the LONG version of what it says there ...
If your pattern has more parts to the bodice, you'll use these same steps for all pieces around the midriff. Choose a location where there is relatively no fussy lines or decoration to deal with. Choose a location below the bust. Shorten above the bust if your bust point is high in relation to the pattern. Measuring is the only way to know the difference.