4 foundations of mindfulness I'm a bit confused about when and how I am supposed to practice each of the four foundations?  Do I do it all at the same time or do I break it down into different activities etc? Can someone please clarify?
In becoming a Bhikku with an idea of performing the practice of breathing towards samatha and vipassana (calm and insight) without first attempting kayagata-satipatthana (mindfulness as regards the body), resembles an owner who yokes the still untamed bullock (an adult bovine animal) to the cart or plough without the nose-rope. Such an owner would find oneself unable to drive the bullock at his desire. Because the bullock is wild, and because it has no nose-rope, it will either try to run off the road, or try to break loose by breaking the yoke. So first and foremost comes the practice of Mindfulness of Body – Kayanupassana. 

Practice of mindfulness of body is to overcome the drudgery of binding concepts and views that we form about it.  To see the body as it is and to realize what it actually is.  So instead of looking at this body as a beautiful body, ugly body or eternal body a person learns to look at the body as it is and avoid the mental pains that are caused by looking at it otherwise. There are four major sections in the satipattana sutta. In Anapanasati – one gets to these steps in its correct order:
(1) mindfulness of body (kayanupassana)
(2) mindfulness of feelings (vedananupassana)
(3) mindfulness of mind (chittanupassana)
(4) mindfulness of mental behaviors (dhammanupassana). 

Within the first major section on mindfulness of body there are five meditation methods.
(1) mindfulness of breathing (anapanasati)
(2) mindfulness of postures (iriyapatha)
(3) refelection on internal and external impurities and other vital parts (kunapa)
(4) analysis of four elements (dathu)
(5) reflection on nine stages of a dead body (nava seevaththika)    

In Anapanasati, with the development of kayanupassana the meditator is in a position to bring vedananupassana to completion. Contemplation of feelings is nothing but becoming mindful of feelings: pleasant, unpleasant or neutral. Here he remains focused on feelings in and of themselves, ardent and mindful. By concentrating on anapanasati to a higher degree, he then brings the cittanupassana to its culmination.  Now he would start to develop dhammanupassana (contemplation of mind contents). To explain how to go about practicing each of these factors is not possible as it will take a lot more than a paragraph or two for each.