Surrender means handing over our life to the Divine and living it the way the Divine wants us to live. It implies three things.
The first is to know what the Divine wants of us. Obedience is the first necessity of surrender. This cannot be done until we are ready to renounce our self-will which is largely a fiction created by the ego and desire self in us. It is best if we can become conscious of the Divine Will within us. But since it takes time, it is best to read Her books of Guidance about our attitudes and life and try to put them into practice.
Second, it means to do our work as service to Her and no more for the sake of satisfying our own or someone else’s ego or desires. Towards this end, we practice Niskaama karma as advocated in the Gita and dedicate our actions to God through constant remembrance.
Finally, we regard our life as given to us only to serve the Divine. It means to use all our energies of thought and feelings and will and works as a means and instruments to serve Her. As to our own life we hand over its complete responsibility leaving it entirely into the Divine Hands to do what He wills.
Seen in another way it implies, first, a surrender of our soul and our destiny to the Divine. We chose the goal to which the Divine has called us and the path that leads us to the goal. Secondly, we give our inner beings to Her with an aspiration to change ourselves and our character so that all in us attune to Her. Finally, we give all our actions to Her by having a single goal of all we do as part of Her service.