I would like to start a timer in my common lisp application that after a certain amount of time it will call a certain method. What would be the best way to accomplish this? <
You could use CL's SLEEP, unless you need more precise timing (since SLEEP is permitted to use approximate timing.)
In LispWorks, if more precise timing is needed, one could use LispWorks' timer scheduling interface.
Note that, same as Zach Beane's TIMER, this is not implementation-agnostic.