Hands.. you'll need a guide, try Loomis 'drawing teh head and hands' You can download Loomis's books online if you search.I also suggest reference. There's an entire montage of hand poses of deviant art if your search.
For feet...use a reference. As in google a picture of feet and try your best.
use organizational lines to get an idea for the length and angle that you will want to use to make them realistic. You can also try by starting out with a wedge shape for feet and refining it.
Skullbie and lba are correct, pantsreminder. In addition you have to practice, practice, practice. I'm not being cute here. Many artists fail to improve because even after they track down the references they need, they do not put the long term effort they need into curing their artistic weakness.
If it is important enough to request references then it is important to work on the problem until it is no longer a problem. OR . . . you could, instead, take decades to gradually become better as I did. But I heartily recommend that you do not do it the way that I did.
Umm . . . but if you want a tip, sit in front of a mirror and sketch your hand or foot in various positions OR [since this is the 21st century] set up for digital photographs of your hands or feet [or a volunteer's] in various positions and then sketch, sketch, sketch.
At least with hands and feets, you always have a reference available. "Practice, drawing from life", is my short answer.
Long answer: Although looking at how other people draw hands can be helpful to figure out 'short-cuts", I wouldn't work from "flattened images"- photographs and mirrors tend to do this, and you don't get a proper sense of depth/ perspective. If you want to able to draw 'em straight from your head, you've got to see them in 3 dimensions. Break everything down into geometric shapes/ simple planes, and get used to drawing those in perspective. Devote an hour a day (no matter what!) to drawing your own hands/ feet in different positions. You can't help but get better this way.
It's hard to give specific tips without being able to illustrate it as I go along; plus I'm not tryin' to write a book here or anything. If I had a scanner, I'd send ya my handouts. Not familiar with websites- I think these other folks have that covered. But I can recommend some books (mostly figure drawing/ academic style) if ya want.