Sat Nam! (Literally "Truth Name"--a Sikh greeting)
The way we (Sikh and kundalini yoga practitioners) use most is mantra, typically one of the Names for the Divine or a phrase about the Divine. Some are more absorbing than others. A complicated mantra works better to stop the follow of thoughts than an easy one does.
Word of warning about real life: The mind is designed to produce thoughts. It takes a while to empty. And genuine emptiness is often a sign of depression. Positive emptiness is usually just a calmness about what the mind produces.
So if your character can tell he/she is being probed, the simplest way to handle it is zap the thoughts with a mantra.
The other useful tool is a painful mudra (hand position). Some mudras are astoundingly complex, and some are extremely painful. Maintaining those does control the mind too.
If the person is spiritually inclined, it's possible to tap directly into the Divine vastness and be so absorbed in it that that's all the mind notices. Some beginners can do this, but it's rare for a beginner to maintain that state.
Let me know if you want more information on either mantras or mudras. Or anything else with respect to meditation.
Oh, and you don't have to be in a cross-legged position to meditate. I can do it while washing dishes.
Blessings,
Siri Kirpal