The definition of this word is not easy. There has been too much attempt to define it from the angle of personality knowledge.Service can be briefly defined as the spontaneous effect of soul contact. This contact is so definite and fixed that the life of the soul can pour through into the instrument which the soul must perforce use upon the physical plane.It is the manner whereby the nature of that soul can demonstrate in the world of human affairs. Service is not a quality or a performance; it is not an activity towards which people must strenuously strive, nor is it a method of world salvage. This distinction must be clearly grasped, or else our whole attitude to this momentous demonstration of the success of the evolutionary process in humanity will be at fault. Service is a life demonstration.It is a soul urge, and is as much an evolutionary impetus of the soul as the urge to self-preservation or to the reproduction of the species is a demonstration of the animal soul.This is a statement of importance. It is a soul instinct, if we may use such an inadequate expression and is, therefore, innate and peculiar to soul unfoldment. It is the outstanding characteristic of the soul, just as desire is the outstanding characteristic of the lower nature.It is group desire, just as in the lower nature it is personality desire. It is the urge to group good. It cannot, therefore, be taught or imposed upon a person as a desirable evidence of aspiration, functioning from without and based upon a theory of service. It is simply the first real effect, evidenced upon the physical plane, of the fact that the soul is beginning to express itself in outer manifestation.
(A.A. Bailey, Esoteric Phychology, 124-5)

What part, Oh Pilgrim on the Way.  play you within this scheme?  How will you enter into peace?  How stand before your Lord?

I play my part with stern resolve, with earnest aspiration; I look above, I help below; I dream not, nor I rest; I toil; I serve; I reap; I pray; I am the Cross; I am the Way; I tread upon the work I do; I mount upon my slain self; I kill desire, and I strive, forgetting all reward.  I forego peace; I forfeit rest, and in the stress of pain I lose myself and find Myself and enter into Peace.
(A.A.B., Initiation, Human and Solar, 212-3)