How to control a person experiencing excited delirium?

Medication. The first step is to try to orient the person and quiet him/her down. If that does not work, it may be necessary to use medications: antipsychotics and/or antianxiety.
Hopefully in hosp. Delirium is a medical emergency, and pts experiencing true delirium should be treated as inpatients. If you are talking about agitation in an alzheimer's pt, this is a very different issue, and a variety of meds and psychosocial modifications can help.