At school we did networks, graphs and relations and matrices, but on the exams I did number patterns instead of networks.
I don't really think you would be required to even make a stem plat or draw a histogram or anything like that. Usually it is more or less fill in the missing value or point on the graph.
If you had to do a stem plot though, try to list the data in order or develop some kind of method to oder the data. I just used to go through the list of data, find the smallest value, put it in the plot, cross it off, then work up till I had done the whole thing. Leave bigish gaps between values in case you miss one, so you can easily fill it in, and count the number of data values in both your plot and the data list to ensure you didn't miss any.
Most importantly, make sure you can do all the median/mean smoothing, both of even and odd numbers of points. This is something which they seem to like testing because it needs to be done by eye and with no calculator in the case of medians and is easy to correct. It is one of the more complicated things on the course. Not that it is that hard.