Cautiously: This is the most common and straightforward way to express "with caution."
Carefully: This word also implies caution and is often used interchangeably with "cautiously."
With care: This is a more formal and less common way to express "with caution."
Prudently: This word suggests caution and good judgment.
The best way to spell the word depends on the specific situation and the nuance you want to convey.