m1 [make 1]

In Knitting Without Tears, Elizabeth Zimmerman listed her "make 1" increase as the one she used most often. While there are several versions of the "make 1" increase, Zimmermann's is perhaps the simplest. Just make a backwards loop on the right-hand needle as seen here and on the next row, treat the loop as a separate stitch. It's quick, simple and effective. Make sure to pull your working yarn tight in order to snug that loop up to the preceeding stitch in order to make sure the increase doesn't leave an unsightly hole.

knit into the front and back

Amy, our beloved editor, says her fav increase is of the "knit into the front and back" variety. This particular increase is very neat and tidy with a little decorative purl bump at the base of each increase.

And is done like this:

Insert the needle into the front of the next stitch as normal and knit it, then without removing the new stitch from the needle, re-insert the right-hand needle into the back loop of the original stitch and knit it again. Voila! Two stitches from one.

To make a double increase using this increase, mark a center stitch then knit into the front and back of the stitch just preceeding the marked stitch and into the marked stitch itself on each row in which you are to increase.

There are lots of other options for increases that involve using the stitches in the row below, but I find myself coming back to these two again and again.

Decreases are divided into two categories: right slanting and left slanting.

Left-slanting decreases lean to the left: these include k2tog tbl, ssk, s1, k1, psso.
Right-slanting decreases lean to the right: K2tog is the most commonly used of these.

You may be asking yourself, "is this really so important?" Well, not when the decreases are spaced far apart [as on the crown of a hat, for example. In that case, you'll want to pick your favorite decrease and use it throughout] but if the decreases will be paired, as they are above or as they are for the gussets of a sock, you'll want to use a left-slanting decrease on one side and a right-slanting decrease on the other for aesthetic reasons. It just looks better that way.

K2tog [knit two together]

Insert the right-hand needle into the next two stitches on the left-hand needle at the same time and knit them together as if they were one stitch. In other words, you'll be doing the exact same thing as when you are making a normal knit stitch, only with two stitches at once. Voila! You now have one stitch where there were two.

k2togtbl [ knit two together through the back loop]

Insert the right-hand needle into the next two stitches on the left-hand needle through the back loops at the same time and knit them together as if they were one stitch.

I talked a bit about knitting into the back loop in the Winter 2002 issue of Knitty so might want to check there if you're having one of those "what the heck is she talking about?!?" moments that we all have from time to time.

ssk [slip, slip, knit]

Slip as if to knit the next two stitches on the left-hand needle one at a time onto the right-hand needle, then...

...insert the left-hand needle into the fronts of the two slipped stitches and knit them together. If you look carefully at this last picture and the picture of "k2togtbl" you can see that the end result will, of course, be almost identical ... a left-slanting decrease. There is another decrease called "sl1, k1, psso" or "skp" for short: slip 1 knitwise, knit the next stitch and pass the slipped stitch over the knitted stitch and off the right-hand needle. The result is quite similar to "ssk". You can use k2tog and one of the left-slanting decreases in combination on either side of a center stitch to make a double decrease like the one shown above.

Yet another method of making a double decrease is to "sl 2, k1, p2sso" which leaves a lovely decorative raised center stitch [see left].

For this double decrease, mark a center stitch, then knit to within one stitch of the marked stitch, slip 2 knitwise at the same time, knit the next stitch [the  stitch directly after the marked stitch] then pass the two slipped stitches over the knitted stitch and off the needles. Pretty, isn't it?