Tableau employs good practices for formatting and visualization from the time you start dropping fields on shelves. You'll find that the discrete palettes use colors that are easy to distinguish, fonts are generally acceptable, grid lines are faint, and numbers and dates follow the default format settings defined in the metadata.
The default formatting is certainly adequate for discovery and analysis. If you are focused on analysis, you may not want to spend too much time fine-tuning the formatting until you have moved on in the cycle. However, when you start to consider how you will communicate data to others, you will need to contemplate how adjustments to the formatting can make a difference in how well the data story is told.
Tip
Sometimes, you will have certain formatting preferences in mind when you start your design. In these cases, you might set formatting options in a blank workbook and save it as a template.
Here are some of the things you should consider...