Stemplots are very similar to histograms. In fact, many times you will start with a stemplot and turn it on it's side to create a histogram. General rules for making a histogram:
1. Start with a T. The left side is the stem (which will be a single number) and the right side are the leaves (there may be multiples of these, but always just one digit, listed in order from least to greatest)
2. Using your data set, cut off the last digit. Look at the digits that remain. If there are no more than 10 you are ready to begin. If there are more than ten, you will need to round the number off and cross off 2 digits. If still too many continue with this idea. The numbers that remain become your stems and are to be listed on the left side in order. Do not skip any values, it is important to see if there are any gaps. The numbers that you cut off are your leaves. You may need to make two stemplots. One with the leaves listed and then a second with them put in order.
3. The most important thing is the key. This will tell the reader what the numbers mean. For example: 3 | 5 = 35 or 3 | 5 = 3.5 million is very important.