I thought I'd better write these thoughts down before I forget them.
First of all, I've discovered by watching Knitty Gritty, that I've been doing my knit cast on and probably cable cast on incorrectly. I'd been slipping the newly cast on sts with the needles pointing toward each other instead of pointing in the same direction. The latter gives a twist to the bottom of the sts and makes for a looser cast on. However, for the lace project I'm working on now, I prefer my old method. (The cast on loops aren't as large.)
Secondly, although a slipped st edge look nice for scarves, it doesn't look as good on lace.
(---s1 is slip 1 purlwise with yarn in front ---)
Start each row with s1, k2 and end with k3.
This gives a slipped st edging with the slipped sts facing outward.
Though, .... for a feather and fan shawl, I instead began and ended each row with k1 or more. It remained flat since every very other WS row began with k17 and ended with k16. The alternate WS rows were k1, p across, k1. A garter sitch edging seemed too bunchy for the shawl.
For my latest (lace) knit project:
(RS): s1, k4, ... and end with k4, p1
(WS): s1, (k1 tbl, p1) twice, ... and end with (p1, k1 tbl) twice, p1
This lies flat and gives an edging with bumps plus a little interest and sturdiness to the edge.
For sock heel flaps:
(RS): k across
(WS): s1, p across, end with s1 (for a regular heel flap)
(WS): s1, (p1, s1) across, end with s1 (for thicker heel flap)
(WS1): s1, (s1, p1) across, end with s1
(WS2): s1, (p1, s1) across, end with s1 (for eye of partridge heel)
These give a slipped st edge that lies on the WS of the heel flap. (I like to do knit sts better than purl ones and so figured why not do the slipping on the WS.)
For dishcloths, I prefer not to start rows with slipped sts. However, the one dishcloth I made with a k1 edge didn't lie flat. So, in the future, I'm going to start and end rows with k2 (or more) or else start rows with (k1, p1) and end with (p1, k1) or some repeat of the moss st.
Finally, OfTroy has a nice summary of cast ons in several linked blog entries. (The picot cast on sounds interesting.)