Secret #1: Cast-on and Bind-off really loosely if you're making a garment, socks or hat. I use a needle two sizes bigger than the pattern calls for to accomplish this.
Secret #2: If it's a hat brim, try counter-acting the tendency to roll with #1 above AND binding off purlwise if a knit side is facing you OR knitwise if a purl side is facing you.
Secret #3: I felt things by washing them in hot water with two pairs of blue jeans and a little squirt of Dawn Dish soap. Scrubbing Hot Bubbles = Felting.
Secret #4: Put your item in a laundry bag or zippered pillowcase to avoid fibers everywhere - it all sheds!
Secret #5: Keep a long handled *tool* to fish the thing out of the HOT water. I have a handle from a broken back scrubber that I fish with.
Secret #6: Check often after about the five minute mark - different yarns felt faster depending on the fibers used and the way they are spun. I find looser spin = faster felting. I almost shrinky dinked a hat in 5 minutes because the yarn was very soft.
Secret #7: Really Block the thing. For a hat, steam the heck out of the brim on the wrong side (while the hat is still damp). A steamer is best but an iron over a cotton towel works well.
Secret #8: For a hat, use something that is about the same size around as the hat covered with a dish towel and shape the hat. Pretend its PlayDough and pinch and push and pat until it looks the way you want it to. Pretend you are a Master Parisienne HatMaker and bend it to your will.
why is she wearing that hat inside???
Secret #9: AHA! I am wearing my hat around the house to custom fit it to my head. I sprayed it with plain water and patted it to shape. Now it will dry and fit perfectly.
Secret #10: Do not be afraid! If you don't like the way it turns out, you can soak it in warm water, roll it in a towel to remove excess water, then BLOCK IT AGAIN. My mom's hat took three rounds before it behaved - I was just being too gentle on a mule-spun wool that was very hearty.