That was one of my fun things to do as a kid. The rules are that you can't step on a line at all...so if someone with small feet made up the hopscotch pattern with small squares, you had to tippy toe hop and it was tough. Once you got to the end, some kids said you had to jump and turn at the same time on the top square, whereas other said you just jump off. And even others said you skip the top one. So you had to go over the rules with everyone you played with.
The game starts with the person behind the line and he/she tosses their rock onto square one. Then you hop on one foot onto square two and then proceed to hop on one foot where there is a one square and two feet onto the side by side squares. Once you get to the end, you do it back and then pick up your rock (in this case, you have your one foot on square two, bend over, pick up the rock on square one) and then hop off.
You can never hop onto the square where your rock is and some people say you can't hop onto their square with rocks either.