These are some helpful tips you could follow when creating a dashboard on tableau.
    • Keep it simple! (no more than 5 charts in the dashboard)
    • Have a specific message you want to communicate (focus on what you want to show)
    • Select the right chart form (know its strengths and limits)
    • Use compelling headlines to describe the take-away message of the visualization
    • Use colour, size, and position to help the audience see what is important
    • Find the models you like and use them in your design, or adapt them to fit your needs

CTRL + F1 [Brings back a hidden or closed Show Me Panel]

After selecting your dimensions & Measures . Click on the Show ME Panel.
Tableau will show the best way to represent your data depending on the selections you have made