> Since Ruby does not require a variable to be declared, do people find
> that they often have bugs related to mistyping variable names?
> Now that I am starting in Ruby, I am wondering what others
> have done to avoid the problem.

These sorts of problems happen less often than you might think.  When they
do happen, the trick is to catch them as early as possible.  I do this by
writing unit tests for all of the code I write.

If I misspell a variable name, when I run the test, either the result comes
out to something I didn't expect, or I get some sort of runtime error.
Regardless, with the tests in place you will find these issues right away.

Look into using the RubyUnit or Lapidary unit testing framework.  They are
very easy to use.  These tools are simple, free, and more valuable than you
can imagine.

Hope this helps,
aaron