Cold. Water. Only.
That's basically my motto.
Yes, you can wash superwash items warmer and/or in the machine (I toss my socks in the machine, I'm guilty) but if you want to keep your knits as beautiful as when you just finished them, for the love of the spaghetti monster, wash them by hand in cold water with a mild detergent.
There are enough brands out there you can either wash with, or even leave in and don't worry about. I'm pretty confident you can pick your own favorite rinse, but I will of course tell you the Wool Wash Bars we make are amazeballs and Eucalan is a really great leave-it-in product.
Synthrapol is an industrial strength, pH neutral, liquid detergent used as a prewash and afterwash for dyed or painted fabrics and fibers.
Synthrapol has the unique property of keeping loose dye suspended during washing, thus preventing backstaining while aiding in the removal of excess color.
If you want to make sure with your hand dyed yarn that you keep all the loose pigments away from each other, you could invest in a bottle of Synthrapol.
The larger craft stores (Michaels, JoAnn), some fabric and quilting stores, online retailers (Amazon) and dye sellers (Jacquard) carry Synthrapol.
Personally I hate blocking (I live in a tiny apartment), but I have seen the before and after pics, and unlike tell-sell commercials, these are actually valid.
After you finish a project, block it into shape.
Don't be afraid of stretching your project so the stitches lay flat and correct any weird loopy things that have happened (I always have weird loopy things in colorwork).
There are specialized blocking tools on the market for things like socks, gloves and hats.
For flat garments and shawls you can buy blocking mats.
I have seen people using foam floor puzzles for children (usually they're way cheaper than a special blocking mat set) and if that works for you: awesome!
HOWEVER: Check to see if the dye in the mats doesn't release when the mats get wet / moist.
I've seen some horror pictures of mats that did stain into beautiful white lace prayer shawls
Less awesome when you have a huge cartoon truck imprinted on it after blocking...
I usually pin my knits down with T-pins or when it has a lot of straight edges, I use a lace blocking wire kit to save myself some time and get an even edge.
Do check your pins and wires for any dingleberries and rust. Once when I was in a pinch I just used an old sewing needle to block a shawl and it turns out it had some rust on it. It washed out, but it did mean I had to restart the hell known as blocking all over again.
Storing Finished Projects
It may sound like a no-brainer, but; after finishing a garment, pair of socks, shawl, etc: Store your hand made items properly! Nothing is wore than winter season swinging around to find out that a family of moths have feasted on your beautiful sweater.
How I store my finished knits: In seperate Ziploc bags, or vacuum sealed bags, in my closet. I have a seperate plastic tub for this that I sprinkle with ceder oil (I don't like lavender).
Frequent use items, like socks, are usually fine since you move them around and use them all the time. But the more delicate items that only get worn once a month or such, those you need to take extra care of.
Despite all of the dyes we use at Undercover Otter being light and sun fast, we do advise you to keep your projects out of direct sunlight for extended periods. The sun is a powerful friend and can cause some dyes to discolor.