During the first and last three berachos of shemoneh essrei, it is forbidden to add personal requests, but one may think about them in appropriate places (e.g. “…v’rofei cholim…”). During other berachos, it is permitted to verbally add personal (or communal) requests of the same subject matter as the berachah. A request for an individual should be inserted in the middle of the berachah; for a group of people, at the end, before “baruch atta.” In shema koleinu, one may add a request about any topic.
A request may be made in any language.