When to capitalize:
* Part of a proper noun: If "memorial service" is part of a specific event's name, like "The Smith Family Memorial Service," you would capitalize it.
* Used as a title: If "Memorial Service" is used as the title of a document or announcement, you would capitalize it.
When not to capitalize:
* General usage: When referring to a memorial service in general, you would not capitalize it. For example, "We attended a memorial service for our friend."
Example:
"The Johnson Family Memorial Service will be held at the First Baptist Church on Saturday at 2 pm."
Note: In formal writing, it's generally safer to err on the side of capitalization when referring to the specific event. However, in informal writing, capitalization is less strict.