If you are setting up a user profile for a volunteer to call using phone bank, these are permissions that you will want to turn on for the profile:
CiviCRM: view all contacts
CiviCRM: edit all contacts
CiviCRM: profile view
CiviCRM: access CiviCRM
CiviCRM: access AJAX API
CiviContribute: access CiviContribute
CiviContribute: edit contributions
CiviMember: access CiviMember
CiviMember: edit memberships
CiviCampaign: release campaign contacts
CiviCampaign: interview campaign contacts
CiviCampaign: gotv campaign contacts
Membership is relevant only if you have a membership module.
You will most likely also want to set up a separate Navigation menu for the volunteers.