Think you don't need to know how to work increases and decreases because you only want to make blankets and scarves? Think again--lots of beautiful patterning is created with increases and decreases in both crochet and knitting. Ripple patterns, lace patterns, even some cable patterns will require you to increase and decrease. I wrote about increasing awhile back, so let's talk about decreasing now. There are so many different ways to decrease in both crochet and knitting that I'm going to split the subject by craft. Crocheters, you're up first.
Let's talk about the really simple ways to decrease first: skipping stitches and slipping across stitches. Skipping stitches (usually written "sk next X stitches") is exactly what is sounds like. Let's call the last stitch you worked stitch A. The stitch next to that one will be stitch B, then stitch C, and so on. Now the pattern tells you to "sk next 5 stitches." This means that you will leave stitches B, C, D, E, and F unworked, inserting your hook into stitch G to make your next stitch. Don't worry -- there won't be a big string across all of those unworked stitches. Stitches A and G will snug right up together, gathering the other five stitches underneath them, and you have decreased 5 stitches.
Slipping across stitches (usually written "sl across next X stitches") is similar, but you won't be gathering the stitches. Instead, you're leaving them where they are, either to form an edge (as in an armhole) or to be worked later. You simply slip stitch across the indicated number of stitches. On future rows, you won't count those slips as stitches unless expressly told to by the pattern.
Now we come to the more complicated decreases, the ones I call the "tog" (together) increases, where you're working multiple stitches together into a single stitch. Anything like sc2tog, dc3tog, etc. is a "tog". The tricky thing to remember is that the sc/dc/tc at the beginning of the stitch only refers to the type of stitch you are working, not the stitches from the previous row that you will be combining. In other words, the written out form of "sc2tog" is "single crochet next two stitches together." Those "two stitches" could be single crochets, double crochets, a single crochet and a double crochet--anything that counts as a stitch.
To actually make the "tog" decreases, you begin working the indicated type of stitch into the first stitch of those to be brought together. So if you're working on a dc2tog, you wrap and insert your hook as you normally would to make a dc. Continue working the dc as normal until you reach the point where you would be pulling through the final two loops. Leave those two loops on the hook and start a new dc in the next stitch to be decreased. Now when you get to that last pull-through, you will have an extra loop to pull through, so you'll be pulling through three loops instead of the normal two. If you were working a dc3tog, you would leave that last loop on the hook again, giving you a total of three loops on the hook as you started your next dc in the next stitch, and you would finish by pulling through four loops. The process is the same no matter what kind of stitch you're making or how many stitches you're decreasing: make the stitch as normal except for the last pull-through, leaving one extra loop on the hook for each stitch worked, then pull through all loops on the hook to end the last stitch.
And there you have the basics of decreasing in crochet. Knitters, you're up next! Come back next week for my knitting decrease post.