I am a long-time weekly adorer. Here’s some of what I do (not all in a single session

, unless I’m planning to be there a while—I have stayed at Adoration all night a couple of times).
You can sit there and just gaze at the Blessed Sacrament. I have often been amazed at what comes to me in the silence.
Spiritual journaling. In the past I had done this both during and outside of Adoration, then I stopped (long story) and have only recently started again. It helps me prepare for my monthly spiritual direction meetings. Be sure to use a pen that doesn’t make noise when you write or you might annoy other people.
Spiritual reading, particularly but by no means limited to works about the Eucharist such as Cardinal Burke’s
Divine Love Made Flesh. The Bible is always a good choice too! There are also a few books designed to be used during Adoration—my personal favorite is
Eucharistic Adoration: Prayers, Meditations and Devotions published by the Catholic Truth Society.
Meditation. Many resources exist, but one I’ve found easy to use is the CTS’s small folded card entitled
A Quarter Hour Before the Blessed Sacrament. It contains texts to help the adorer reflect during Adoration. These texts can also be used during longer periods of Adoration, so don’t let the 15-minute aspect put you off.
Examination of conscience. Particularly helpful if you will be confessing soon, perhaps even during Adoration (confession is available during all Adoration times in my parish), but always beneficial even if a confession isn’t immediately in view.
Liturgy of the Hours (prayed silently, of course).
Stations of the Cross (prayed silently, of course).
The possibilities are legion. Hope you find the right devotion(s) for you.