Yes, I got the hang of it eventually, DG!
For really big items (cello, car seat, tripp trapp chair, shed) I've done pickup only, cos I'm lazy and also a bit paranoid about things getting damaged in transit. Plus I have to do school pickups, so can't stay in all day waiting for a courier to pick up. It doesn't seem to affect the price that much, although we are fairly near to central London. I guess it would be more of a disadvantage out in the sticks.
I tend to only list items I know will sell well, I can't really be doing with selling things for 99p. Obviously it does happen occasionally, but I try to avoid it. These are my current items, some of which seem to be doing okay, though the green skirt only has two watchers, so might not sell.
It's worth doing a good bit of research under 'completed listings' to see what does and doesn't sell before you list things. The only things I will specifically buy in order to sell on is the M-B clothing (though all the stuff in the current listing is my own dc's outgrowns, or unwanted hand-me-downs). I have several boxes of meccano sitting in my study that I'm currently dithering about.
Have you tried car boot sales? Also good, but you have to get up v. early and things do go for depressingly low prices. I know expatinscotland recommends Gumtree, and I was thinking about giving that a whirl for items I can't be bothered to ebay.