When does a lead become a member of a program?

[Kathi_Gosche]

At what point does a lead become a member of an email program? Is it upon sending them the email through a campaign within the program? Or is it based off some other action?

[Anonymous]

Upon changing their program status:
https://community.marketo.com/MarketoArticle?id=kA050000000LAASCA4

[Josh_Hill13]

A lead may also become a member if they fill out a local form.

[Kim_Allen]

This may be helpful: https://community.marketo.com/MarketoTutorial?id=kA250000000KyssCAC