I would like to make a line graph with markers that does something seemingly simple, but I can't seem to find where to make the necessary changes. I have a graph that has two lines of data. I'd like to have the markers be different for each line, like rectangles on one and diamonds on another. Is this possible?

As a caveat, that can end up going wrong.  Crystal does a lot of automatic formatting of its charts.  When your data changes, it could potentially end up changing the size of one chart, and not the other.  I've had that happen before when I tried to do this.  If you have a static Y-axis (say, a percentile graph), then it's less likely to be an issue.  But, it's something to be aware of.