The Satipatthana Sutta, the discourse on the foundations of mindfulness, is generally regarded as the buddhist text with the fullest instructions on the system of meditation technique unique to the Buddha himself.
The practice of Satipatthana meditation centres on the methodical cultivation of one simple mental faculty readily available to all of us at any moment.
This is the faculty of mindfulness, the capacity for attending to the content of our experience as it becomes manifest in the immediate present.
Sati = mindfulness. The minute by minute, present moment awareness.