Turning an exponential graph into a line graph

Hi, in physics we did an experiment which would determine the acceleration due to gravity. we dropped a golf ball from a table and made a d-t graph and all the good stuff. My teacher said that as one of the methods we must manipulate the graph so that the outcome is a straight line from which we can find the slope ( not a secant or line of best fit). Can anyone please tell me the best way to change an exponential graph into a straight line graph?

- Thanks