Blocking Acrylic Yarn
Unlike natural fibers which can be blocked by simply shaping the item while wet, blocking acrylic requires heat. Many people try to wet-block acrylic the same way they would do wool, and they aren't happy with the results so they conclude (incorrectly) that there's no point in blocking acrylic. That's not true. There's simply very little point in wet blocking acrylic. The simplest heat-blocking method is to run the item through a washer and dryer. That's the easiest way, so I recommend trying that first. It should even out any slightly wonky stitches. If you're happy with the appearance at this stage, no further effort is required.
A more intense way is steam blocking. If done correctly, blocking improves the appearance of a knitted item. It smooths out minor irregularities in stitch size and overall makes the item look more polished and professionally produced. It can also prevent edges from curling. Here's how:

Lay the knitted item out flat. Stretch, smooth and smoosh it until it's the shape you want and the stitches are nice and even. If it won't hold its shape on its own, use pins and/or blocking wires to hold it in place.

Use a steam iron to steam it. Hover over the fabric with the iron, not touching it. As you go, pat the fabric gently to smooth it out (in areas where it wasn't already sitting smoothly).

Once you're done, the blocking is permanent. Don't be scared off by the word &quot;permanent;&quot; it's actually a good thing because it means the gift is low-maintenance. Your gift recipients can toss it in the washer and dryer without needing to block it again.



Tips:

Wash your item before steam-blocking it. A knitted item usually needs to be washed after knitting, because your hands aren't always completely clean when you knit (and even when they are they still have natural oils on them). If you steam block a dirty item, you can end up setting oils and stains into the fabric.

Knit a swatch from the same yarn (if you made a gauge swatch, just use that). Practice steam blocking the swatch until you get the hang of what distance to hold the iron from the swatch, and for how long to steam it. Actually try to over-block part of your swatch to the point of &quot;killing&quot; it - that way you know what it actually takes to kill acrylic, and you can avoid doing that. You'll find that it takes a lot more heat than you would expect to kill acrylic.

Irons often have some build-up of calcium salts in their steam holes, especially if you left water in it the last time you used it. The build-up will leave annoying little white crumbly bits on your beautiful knitted item. Run the hot iron over a towel to remove some of the crumbly bits before using the iron for blocking.

&quot;Killing&quot; acrylic is actually an intentional technique that is done on purpose sometimes. Usually for lace. It apparently gives the fabric a lovely drape, but removes all the elasticity. It's probably not appropriate for your cabled scarf, but keep it in mind if you decide to make lace someday.

Ravelry has some very helpful discussion groups about working with acrylic yarns, eg I don't care who knows...I love acrylic!.

If you love working with acrylic, consider investing in a steamer. They work better than a steam iron.