Adding visual effects to slides can sometimes make PowerPoint presentations be more interesting. Keeping a reasonable amount of effects per slide can usually aid the comprehension of the material and make it easier to memorize.
To add visual effects to text, images, charts, and other objects, first go to the top menu in PowerPoint and click on the "Animations" tab.

 
Following, click on the "Custom Animation" button, located right next to the "Preview" button on the very left side. 

With the click on "Custom Animation", a new menu opens up on the right side. It enables you to add effects to the objects in your PowerPoint presentation.

 
To add an effect to a particular object in your presentation, first select the object by clicking on it. The top button "Add Effect" will now become active and you can choose from a wide variety of effects.

 
Once you have selected the effect, you can further adjust the settings of the effect:

 
   a) You can adjust the start of the effect
           -if you want the effect to start with a click, then select "On Click" (this is the default setting).
           -if you want the effect to start automatically after the previous one, then select "After previous" from the drop-down menu.
           -if you want the effect to start automatically with the previous one, then select "With previous".
   b) For some effects, you can adjust the direction of the effect.
   c) You can adjust the speed of the effect:  very slow, slow, medium, fast, very fast. For most effects, fast is the best option.
 
You can add different effects to different objects by using the methods described above.