A 3-year-old can clean up his toys, as long as that means tossing every toy on the floor into one box. He can sort and separate things too, lining up his building blocks in one row and his cars in another. (But then he won't want to pick them up and put them away, because now this is his creation, to be stepped over and admired for at least another day!)

He can "make" his big-kid bed (i.e., pull up the blanket haphazardly and tuck his bear under it), but don't ask him to do it if you can't stand looking at an unkempt bed. Whenever I pass my 6-year-old's room, I can almost never resist the temptation to go in and remake her bed. She can always tell I've been in there and gets highly insulted, so I give her other chores that I'm not as picky about or that she's more adept at.

While your child is little, you'll want to praise his efforts more than criticize his performance, especially when he remembers on his own to do a chore, even if it's just capping the markers after using them. As he grows, it's fine to offer a bit of coaching now and then, to teach him the best way to do things ("See how I smooth out the laundry before I fold it?"). You'll be showing him that being responsible pays off in the satisfaction of a job well done.