To avoid pilling, we recommend hand washing your sweaters, especially those that have looser textures, applied embellishments or openwork patterns. For those that are machine washable, at least turn them inside out before tossing into the washer. If you have a pilling problem already, you can use an electric piller/fabric shaver (found at stores like Target) that runs on batteries or through a wall outlet.
Electric shavers are a great way to take 'five o'clock shadow' off your knits.
Fabric shavers are easy for removing pills on a flat knit, but they should not be used on knits with naps, textures or lofty surfaces. For any snags or loose ends of yarn, you can easily remedy this with a "knit picker". These are hook-like tools with an eye that draws the yarn from the outside of the garment to the inside. They're sold at sewing shops.
To avoid stretching your knits out of shape, it helps to be aware of their stretching limits while you wear them, but the most common over-stretching happens in storage rather than on the body. Because of this, we fold all knits flat for storage rather than hanging them. Hanging a sweater on a hanger can develop stretched-out humps at the shoulders where the knit has pulled down over the hanger's "shoulders" over time. This is most prevalent with heavy sweaters on narrow hangers (wire hangers are a sweater's death sentence), but it can even happen with lightweight sweaters, particularly if stored in more humid climates.
A knit picker. This convenient tool is great to keep in your handbag.
The dreaded 'hanger hump'.
If you need to hang your sweaters, use padded, thick hangers that match the width of the knit's shoulders. For shoulder-less items (like tube tops) and heavier or longer items (like dresses or beaded sweaters), use a hanger with a bottom bar so that the knit can be folded over and hung from the bar. This more evenly distributes the weight of the knit, so it's less likely to stretch out. The savviest clothes-horse will cycle her knits by season, so that any knit in the closet is hung up only while in active use, and then stored folded the rest of the year.
If, despite your best efforts, there's an overstretched knit in your closet, you can always block it. Blocking just means shaping a knit into a certain size. To do this, place the sweater in a barely warm tub of water (use no agitation for animal fibers, especially for woolens), let it soak up the water, and then gently press out the water into a sink (do not wring or twist). For out-of-shape portions of knits, you can dip the overstretched areas in warm to hot water, to encourage shrinkage in the specific spot, but be careful not to over-shrink. Once it's not dripping, place the knit onto a padded towel (two or three layers of towels is fine), and mold the knit with your hands into the shape you want. Once it's in place, use rustproof pins to hold the knit in this shape, pinning knit to towel. Let it dry and the knit will "magically" become the shape you've molded.