I am trying to write a trigger that will add points to a custom field within Leads based on the subject and created by id of a task.  These points would need to accumulate on top of each other over time.  I am completely new to writing triggers and am looking for any recommendations or starting points.

I am trying to write a trigger that will add points to a custom field within Leads based on the subject and created by id of a task.  These points would need to accumulate on top of each other over time.  I am completely new to writing triggers and am looking for any recommendations or starting points.