Honestly, this becomes a problem when functions are trying to do too much. There's almost always a better design pattern when you see a function grow to more than a few parameters (usually it's the poor guy that inherited the old code, and appending parameters is this quickest way to "get the job done").
Elusive's answer is the best according to your question, but take a look at cyclomatic complexity:
http://en.wikipedia.org/wiki/Cyclomatic_complexity
This is a good way to know if your function is doing too much, which makes your question less of a problem than it probably is now.
