Sets enable you to visualize groups which match one or more criteria. They are even more powerful in combination with parameters which allow you to dynamically change the criteria for the sets.
You will often get into a position in which you will have to spend some time on cleaning the provided data before you can perform actual analysis on it.
The last() function can be very helpful when you want to highlight a single data point of your data series. May it be the last, second last or even the first point of the series.
You can save your audience some head leaning if you make your y-axis title horizontal instead of vertical. By default the y-axis title is vertical in Tableau and it is not possible to change the alignment to vertical. But with a little trick you can change that.
Marginal histograms are excellent for displaying your data on multiple aggregated levels in one view.