satipatthana

Strong perception
In order to be mindful of an object, strong and firm (thira) perception of it is necessary.As much as perception(sanna)is firm strong and steadfast,mindfulness will also be firm,strong and steadfast.
The two functions of perception are the recording and the recognition of formations(sankhara),irrespective of their wholesome or unwholesome nature.sanna is compared to the recording of talks with the help of a tape or video recorder. The recording takes place regardless of the content or quality of the talks. A clear, high quality recording,such as a state-of-the-art digital recording on CD of a classical concert or opera,is the cause for a clear,strong,impressive listening experience(mindfulness)when replaying the recording.
Similarly,in the meditation practice a strong,clear-cut perception(nothing or labelling)of the arising objects of observation is very supportive of strong,clear-cut,steadfast mindfulness.

Four foundations of mindfulness
Another proximate cause for the arising of sati is the four foundations of mindfulness(kayadisatipatthanna padatthana). That is,mindfulness itself is the cause of mindfulness.In fact, the development of mindfulness is the result of continuous momentum,one moment of mindfulness causing the next.
This can be compared to the process of acquirnig an education,assuming that student is studious and does his homework respectfully.Lessons learnt in the lower grades are a cause for learning lessons in the higher grade.Primary school education is a cause for high school education,and this is turn serves as acause for tertiary and university education.