Do you include service as a part of your expectations of your submission?
Yes, I find it difficult to picture a lifestyle D/s relationship without it.
How do you define service?
I've never tried to define it directly. What I write next may be inadequate but I will do my best.
I would define service as acts provided for the benefit or pleasure of the Domme that do not provide direct pleasure for the sub. e.g. sex provides sexual pleasure and physical intimacy for both parties, so it would not qualify as service.
Giving a Domme a pedicure provides her with a benefit but it does not give the sub "pleasure" in a traditional sense (unless they are a foot fetishist). The pleasures the sub derives from giving the pedicure, such as feeling useful and being happy to please her are ancillary and not the intended goal of the action. This would make the pedicure a service.
Under this definition service can cover a variety of types of acts including domestic tasks, pampering/waiting on, and sexual act that are performed strictly for her benefit.
What does it mean to you?
This hits on so many levels.
Service is a means of showing my love and devotion to her.
Service is a measure of my effort and attitude. Performing my tasks to a high standard, in an appropriate amount of time, and with proper enthusiasm reflects upon my quality as a submissive.
Domestic service is my role. The thought of her having to perform mundane, tedious, and unpleasant tasks, pains me.
My domestic service gives her more pleasurable leisure time to enjoy herself, so it directly contributes to her happiness.
I could keep going but this will eventually get boring.