My first submissive act was when my husband and I had been dating for awhile, and were newly intimate with each other.
We were in his bed, with him reclined against the headboard and me lying against his chest. He would carress my body in various ways and locations, and ask me if I enjoyed what he was doing, to which I (of course!) would respond "yes" or give an approving "mmm".
He then reached for my hand, which was resting on his thigh, gently picked it up, and placed my fingertips over my clit. With his hand resting on mine, he slowly began forming slow circles.
He kissed my ear, whispering, "Does that feel good?" I rested my head back on his shoulder, saying it did. Then, he took his hand from mine and told me he wanted me to make myself cum for him.
I was a little uneasy with this, as I had never masterbated with someone watching before. I was already stimulated from our foreplay though, so the surprise of his request had pushed my excitement even further.
Knowing that he was watching and feeling my body respond to self stimulation brought me to one of the best orgasms I had ever given myself.
Since then, we have had many pleasurable new experiences together.