Chapter 7 of the APA Manual is devoted entirely to using tables and figures, how to create them, positions, labels, and present them in your writing and publishing.
Tables (and figures) should be understandable without reading the text of the article. However, they also have to relate to the text and are expected to be referred to at least one time within the text of the paper. Often, tables and figures are explained in more detail in the text as well. BUT, tables and figures still must be understandable on their own with no extraneous information.
A general rule about tables is this saying, "Table top". This means that the text with the table is explained at the top of the table. But with figures, the figures explanatory text is at the bottom of the figure. However, explanatory "notes" can also be added below the table
The text in the APA manual has a wonderful checklist to use when creating tables on page 207
components of a table:
There is a wonderful "Table Checklist" on page 207 of the manual.
An example of a basic table (Table 1) can be seen below. If you are submitting to a journal, be sure to use the journal guidelines for tables. The highlighting is not APA formatting but was added here for clarity.
table number: table 1
table title: The collection of plants in my front yard
table headings: Plant, Quantity
note: this table was made using Microsoft excel. top and bottom borders were added to the "Plant" and "Quantity" row, and a bottom border was placed on the "Ferns" row. A simple line is all that is needed in your tables such as this. Italics are used for the table title.