If you have a series of elements in the body of a paragraph, separate each element with lowercase letters enclosed in parentheses. Although only necessary for more complex elements, here is a simple example: (a) lions, (b) tigers, and (c) bears.
Only use numbers to separate elements in a series if in a vertical list.
This would be appropriate when you need to show a specific order of elements, such as in steps in a procedure or conclusions.
Sixth edition APA now allows for bulleted lists. Bulleted lists are appropriate when presenting a list of items in no particular order.
The bullets indicate that I like apples, bananas, and oranges equally.