Arabic numerals, e.g., 1, 2, 3...
\renewcommand{\thefootnote}{\roman{footnote}}
Roman numerals (lowercase), e.g., i, ii, iii...
\renewcommand{\thefootnote}{\Roman{footnote}}
\renewcommand{\thefootnote}{\Roman{footnote}}
Roman numerals (uppercase), e.g., I, II, III...
\renewcommand{\thefootnote}{\alph{footnote}}Alphabetic (lowercase), e.g., a, b, c...
\renewcommand{\thefootnote}{\alph{footnote}}Alphabetic (uppercase), e.g., A, B, C...
\renewcommand{\thefootnote}{\fnsymbol{footnote}}
A sequence of nine symbols (try it and see!)