Ok, here's a plan--
find a stitch dictionary (treasury, collection--what ever you want to call it.)--use a library, or look on line (here! and else where!)
find some lace stitches you like.
and then find some old VRC tapes (the older the better--get some at garage sales (or the trash)
crack them open.--the tape is a great 'fiber' for knitting.
Knit yourself some grocery/"green" tote bags from the tape (so much better than spending hours cutting up plastic bags.. tape is ribbon like, hard to break (super strong!) and not bad to knit with.
make some lace tote bags!
these will be your swatches.. (don't like the stitch? don't frog, just trash!)
find and practice knitting a stitch you like (tote bags work best in a lace pattern--it makes the knitting stretchier!)
Then buy some nice (or even simple kitchen) cotton--(ie sugar & cream, Peaches N cream, Bernat crafters cotton.. what ever) Or if you want buy some mercerized (shiny polished cotton) and make your curtain.
First make a wash cloth (for a swatch!)
Start with a simple loop cast on (yes, it will be loose and messy looking.. you want that!)
make 2 or so inches of stocking knit.(end with a purl row.)
then take a much smaller circ (say a size 3 or 4 circ (20 or so inches long.. but length doesn't matter much)
pick up those loose loops on cast on edge (it will be easy with a smaller needle)
(count, and make sure you get one loop per stitch (WARNING>> if you do it right, you'll be 1(one) stitch short.. --so if you cast on 100, you'll only be able to pick up 99 stitches)
Here is where the loose messy cast on works to your advantage--it makes it easy to pick up stitches!
(and as you do, you'll 'tighten them" and make them neat and attractive at the same time!)
fold knitting (right side out) and hold knitting so the fold is at bottom, and smaller needle is in back
Now you are ready to knit:
stick right needle into first stitch (on needle) and then into first stitch on circ--and then knit these 2 stitches together..
Repeat! the last stitch won't have a mate--just knit it.
now you have made a 'casing (or hem) for the curtain rod! See it was that easy..
(not sure? cast on 20, knit 2 inches, pick up 19 and try it as a swatch!)
then, with the curtain rod casing knit, start your pattern! (lace pattern)
You could even practice with the VRC tape and make a tote bag with a drawstring top(and thread a cord into it)
(just be sure when you sew up sides of bag not to sew casing shut!)
you'll have practice knitting lace (and be honest, if there is mistake in a tote bag knit from VCR tape will it matter? just work 2 or more rows of stocking knit, and return to pattern (don't bother frogging--just work on learning the lace pattern!)