Sharepoint 2007: How to update an item of the attached library within a Workflow?

I am new user to SharePoint and creating a Workflow where an item in the attached Library needs to be updated upon certain conditions. The SharePoint Help tutorial mentions not to update a data field in the current Library or List, as it would create an infinite loop. Then what is the proper method to update a datafield in the current attached Library of the Workflow? (The Library Workflow is initiated on new item creation and item modification).

If I Set an item in the current attached Workflow Library, to a new value... will the Workflow get started again? I am trying to ensure this doesn't happen. Should be simple question, but I am unsure at this time. Thanks in advance.