Having completed the preliminary practices there are two main ways to go, which are often combined these days. The first way is described as a path of skilful means and it involves doing practices that use mantra and visualisation, generally known as 'deity practices'. The second way relates directly to the nature of mind and is a graduated system of practices, involving calm abiding and insight meditation, leading to Mahamudra realisation of the true nature of mind. In general deity practices are developed to their fullest in the long term retreats (such as four year retreats), while the second way is found in Mahamudra courses offered by high lineage teachers in the Karma Kagyu tradition.
With regard to deity practices, it is important to explain that the concept of 'deity' in Buddhism is different to its traditional usage in the West. It does not refer to a separate, external, supernaturally powerful being that we pray to in order to receive grace and favour. Instead 'deity' in this context refers to different facets of the enlightened mind that are within us - for example, limitless compassion. Deity practices normally involve meditating on a particular form, which is an expression of a quality of enlightened awareness. To use an analogy, if our Buddha Nature is likened to a translucent diamond composed of light, then the different deities, like Tara and Chenrezig, are like different facets of this diamond, expressing different qualities of the enlightened mind. When we meditate on a deity, it is like establishing a mind link (yidam) with these qualities; and through meditating on the deity, these qualities gradually manifest in us. For example, Chenrezig is regarded as the embodiment of limitless love and compassion, and through meditating on his form and reciting his mantra, limitless love and compassion gradually arise in us.
Normally our teacher will recommend a practice to us as that will be most effective in purifying our particular type of negativity and bringing out our unique, positive qualities. Each deity practice requires an empowerment, which is a formal ceremony that opens the door to that particular meditation practice. It is both an authorisation to do a practice and it initiates us into the main elements of the practice. After having received the empowerment (called 'wang'), we then receive the scriptural transmission to recite the text of the practice (called 'lung') and then detailed instructions on how to do the practice.
At its most profound level an empowerment can confer upon a student, whose mind is ripe and open, a direct experience of the true nature of mind through the doorway of that particular practice. This happens by way of a ritual that bypasses the sceptical rational mind and transmits directly the heart essence of the practice. In order for an empowerment to be effective the teacher needs to have been authorised to confer empowerments by his teacher, who must hold an authentic spiritual lineage, and the student needs to be open and receptive and have faith in the process of empowerment.
Our everyday mind is like a curtain obscuring sunlight coming through a window. The sunshine represents our Buddha Nature and the curtains are our limiting habitual tendencies. At its most profound level, during the ritual of empowerment it is as if our spiritual teacher walks over to the window and pulls back the curtain so that the sunlight streams into the room, illuminating everything. Previously, we had just heard about the sun, but we had never seen it or experienced it for ourselves. Now, even if it is just for a moment, we see it with our own eyes and feel it on our skin. At first, this experience of the sunshine is short-lived. Our old habits of thinking and reacting flood back and the curtain closes again. But at least we have seen the sun. We have perceived our Buddha Nature behind the curtains of self-centred thought patterns. Then, on the basis of having experienced the sunshine directly, we do the deity practice for which we have received empowerment, and this gradually stabilises the experience until it finally matures into full blossoming of our Buddha Nature.