Waist shaping is one of the single most important things you can do to get a fabulous-looking sweater. Whatever your shape.
Done the traditional way, decreases and increases are worked at the side edges of your body pieces, creating a garment with hourglass-shaped sides:

(Typical decrease row: Knit 1, ssk, knit to last 3 stitches, k2tog, knit 1.)
This kind of sweater looks great on a table, and kind of works if you have a curvy-shaped waist (that is, you look hourglassy from the front). But for many of us, this kind of waist shaping is problematic: It removes fabric from a place where we don’t get smaller. (I’m quite straight in the waist, for example:)

But that doesn’t mean that we should skip the waist shaping! In fact, the opposite is true. Hand-knit fabric is thicker and more substantial than what we’re used to in the store, while at the same time it’s typically less dense for the size of the yarn. (After all, you’re generally not willing to knit as tightly as a machine can.) So while store-bought knits might move and float around you in a wonderfully figure-enhancing way, your hand-knits typically will not. In fact, your body takes on the shape of that sweater, not the other way around.
So if you don’t want to look like a box, you need waist shaping. The solution?
Take advantage of the fact that knitting is sculptural, and create a 3-d piece of fabric by working your waist shaping in the center of the piece. This kind of waist shaping is no harder to work – you’re working the same kinds of shaping, just in different locations:

(Typical decrease row: Knit to 2 stitches before first marker, ssk, slip marker, knit to next marker, slip marker, k2tog, knit to end.)
Voila! Shaping that removes fabric where you get smaller, resulting in a gorgeous and flattering fit. (Bonus: Since the decreases used slant inward towards those markers, the stitches in the center stay nice and straight, and you get lovely subtle hourglass lines on the sides. Very nice!)
Shaping this way comes with another big advantage, too:
Since the shaping is away from the side seams, the front and back of your sweater don’t need to match.
Need extra width for a bust? No problem! More increases on the front of your sweater than on the back. Have a bodaciously awesome backside? No problem! More decreases on the back of your sweater than the front. Carry more weight in your front? Shape the back, and leave the front straight to the armholes!
In fact, you could make your stitch counts at the hip, waist, and bust totally different on the front and the back, with no result other than a fabulous sweater.

To give this method of waist shaping a try, you have a couple of different options:
- If your pattern already has waist shaping written near the side seams, you can work it at the same rate as specified in the pattern, but in a different place:
- On the back, place two markers each 1/3 of the way in from the sides (1/3 of the stitches in between the markers).
- On the front, place two markers each 1/4 of the way in from the sides (1/2 of the stitches in between the markers).
- Each time a shaping row is specified in your pattern, work it as written – except work the shaping at the markers, as above.
- If your pattern is written with no waist shaping at all, the first thing to do is decide how many stitches you’d like to remove. You’ll work half as many decrease rows as you have stitches to remove.
- Calculate the number of rows you have for shaping by taking the sweater length to your waist, removing the height of any trim, and multiplying by your row gauge.
- Divide the total number of rows by the number of shaping rows. This is how often you’ll work your shaping.
- Once you know your rate of shaping, place markers and shape as directed above.
Of course, CustomFit always uses this method of waist shaping, exactly the way you need it. So if you’re working from a CustomFit pattern, you don’t need to worry about any of this.
Regardless of what pattern you’re using for your next sweater, though, I hope you’ll give this method of shaping a shot! It’s super simple, and makes a world of difference.