For a 16 oz. takeout cup:
With worsted weight yarn and a G hook, chain 30.  Join into a ring and hdc into each chain.  Increase 2 sts every other round (e.g. inc 1, hdc 12, inc 1, hdc rem), checking the fit every once in a while, working a plain round to tighten it up if necessary. I like a cozy about 6 rounds high.  Stretchy yarns like wool need fewer increase rounds – increasing 2 sts every third round might do the trick.  If you want it to fit lower, start with a shorter foundation chain.

Found info on where to find the pattern here:

http://www.craftster.org/forum/index.php?topic=308423.0