I'm not sure whether I am going to turn from knitting shawls to something else -- newborn baby clothes perhaps? -- but in either case I wanted to write a little about different types of shawls and what I've learned in the last month or so.
First of all, there is a super simple type of shawl where you just knit back and forth increasing on the second or third stitch of every row. It makes a basic triangle. I knitted a shawl like this when I was first learning how to knit, in garter stitch. I ended up frogging it, though, because I didn't wear it. The shape made it too hard to keep on over my shoulders.
I did use the same pattern, however, to make a few quick head or neck kerchiefs. If you grow it outwards towards the end of the work, at the top, by increasing at the beginning and end of every row instead of just the beginning, you have an easier time tying it around your head or neck.
Even simpler is the rectangular prayer shawl, where you just knit back and forth until you decide you are done. And of course there are simple rectangular scarves. I made several of the latter when I first learned to knit, too.
You can knit rectangular scarves either sideways (up and down) or across (horizontally). You can join them to make cowls or infinity scarves. I learned that you can shape them to make them more like shallow shawls, by working sideways -- starting with less stitches, grading upwards to the maximum width by increasing as quickly or slowly as you like, then decreasing in a similar way at the end of the work. I used this form to try out lace stitches because I didn't have to do the math involved in a horizontally symmetrical shawl with lace.
Then I learned how to do the other kind of triangular shawl. In this one you cast on an odd number of stitches, and place markers around the center stitch. Then, you increase on the second or third stitch at the beginning and end, and also increase (usually with a yarnover) before and after the center stitch. This makes the beginning and end of the rows into the top of the shawl. A triangle forms outwards, which means you can make lace borders or other things at the end of the work instead of the beginning. You can also make the triangle shallower by increasing at the beginning and end of the wrong side rows (which you don't do if you want a deep traditional triangle).
These are not my favorite kind of shawls, but they make it possible to have some beautiful effects.
I generally like the thinner more flowy type of shawls, that you can make into head scarves. One type that I have done is the crescent shape. Often you start with a garter tab, presumably to keep the center stretchy. The ones I have done start from the top, like triangular ones, except that you increase evenly rather than just at the center. You can border them with lace.
I really like the type of shawl that starts at the side with 4 stitches cast on and then go at a bias. You increase at the beginning of the right side and then decrease at the end of that same row. Then, on the way back on the wrong side row, you increase at the end of the row. So your work ends up with an assymetrical shape between a triangle and a curve. It grows in one direction and decreases at half the speed in the other direction.
Finally, there is a way of doing a simple bottom up triangle that has the virtues of the more shallow, wide, flowy types of shawls. In this method, you cast on a given number of stitches at the beginning of each row -- say 4, or 6, sometimes more. If you have a stitch pattern that is worked over that number of stitches, you can have very pretty results with very little counting or calculating. Kriskrafter has several very pretty and easy to work patterns using this method.
There are a few other methods that I would like to try. Elizabeth Zimmerman has a "Pi" type circular shawl. It is worked in the round, but regular increases similar to what you do for a top-down beanie or beret keep it lying flat. Another thing I would like to try is to bind off the edge of a shawl and then work a lace edging back and forth by picking up stitches.
Something I have learned is to use larger needles than called for by the yarn. That makes the fabric looser, which is not good for things like socks, but is very good for most shawls. I also learned you can usually adjust the size of a shawl pattern easily by using more or less yarn. That means you can use the spare skeins hiding in your stash. I learned that it's fun to experiment with different types of yarn than called for by the pattern, but your results may vary. Sometimes color combos or yarn combos that look great in my imagination look shoddy on the needle. I usually start over if I'm not happy with how something is going.