How do I use footnotes in AMA style?

The AMA manual of style (4.1.4.3) states that footnotes may be used to provide additional explanatory information about a table or figure however page footnotes should be avoided if information can be included in the text. Use bottom-of-the page footnotes sparingly.

AMA style uses superscript numbers¹ for referencing. 

Superscript letters^a are used for notes in tables and figures.

Superscript traditional symbols* are used for footnotes to clarify information at the bottom of a page.  

Table & Figures (Notes)

Footnotes can be used to describe information in a table or cite references.

• Descriptive footnotes are indicated with superscript lowercase letters in alphabetical order (a-z) listed at the bottom of the table or figure. See example below with footnote b
• To cite references for information used in the table. See example below with footnote a and superscript number 28.

 Page Footnotes 

For bottom-of-page footnotes, use the traditional symbol sequence: *, †, ‡, §, ¶, #, ||,**, ††, ‡‡, §§, ¶¶, ##

In Word, open the Footnotes menu under the References ribbon and click on the "Number format" drop-down, and scroll down past the Roman Numeral options to find the symbol sequence.

Examples:

In text: 

• The symbol goes after any punctuation marks such as commas or full stops (but before a colon).

.........Pierre Krystkowaiak.*

........dataset^† ,

Bottom-of-the-page footnotes:

• Symbols are not superscripted at the bottom of the page.
• Each footnote at the bottom of the page ends with a full stop.

*Correspondence to Pr. P. Krystkowiak, Department of Neurology, Hospital Nordwest, Frankfurt. 

† Data were obtained as part of an investigator-initiated trial program research grant.