Take the time to use them correctly and effectively. Tables Tables are a major source of presentation complaints. Use only a few rows and columns. Label all columns with meaningful labels. Include measurement units where necessary, such as degrees Celsius, meters, people per square kilometers, etc.
Metric units are preferred.
Use color, italics, underline or bold face to highlight numbers of importance, especially if you want to draw the audience's attention to them while you are talking. The table should not fill the whole display area. Leave large gaps at the edges to allow for low screens and obstructed views. If you cannot understand your graphic - neither will your audience. Keep it simple and sparse.