In virtually all of our sadhana practices, there is some form of self-generation practice. Self-generation practice, in short, is training in dying and being reborn as the deity.  One of the most common definitions of samsara is “uncontrolled rebirth.”  Without freedom or control, we are thrown from one samsaric rebirth to another.  Attaining liberation from samsara, therefore, is taking control of the death process so that we can take rebirth in a controlled way as a deity in a pure land.  Our training in self-generation as the deity is the method for gaining such control.  If we learn how to die and take a pure rebirth in our practice there is a high probability we will be able to actually do so at the time of our actual death.  There are two reasons for this.  First, every time we train in self-generation, we create new karmic pathways in our mind from our present state to the pure land.  It is like the constant flow of water along the same path will gradually form a canyon.  It is like a path that having been travelled many times is easily followed.  We, in essence, dig our escape tunnel out of the prison of samsara.

Before we engage in self-generation, the first step is always the same:  we dissolve the guru into our heart.  We find this in many sadhanas.  This can be likened to us having a mind transplant.  The mind of the guru deity becomes our own.

After we dissolve the guru into our heart and mix his mind inseparably with our own, we usually then dissolve all phenomena into the clear light Dharmakaya.  I have found it helpful to maintain the following recognitions as I do so.

We can understand this as follows:

1. The things that I normally see do not exist at all, and they have completely dissolved into the clear light of my very subtle mind.  The things that we normally do not exist at all and are actually just illusions, or holograms within our mind.  We should imagine that all conventional phenomena dissolve into the clear light emptiness of our very subtle mind, like a dream that ceases.
2. This completely purifies all of the contaminated karma that gives rise to my personal samsara.  All appearances arise from karma.  Our samsara is a mere karmic appearance to mind.  When we connect with the emptiness of a phenomena, it functions to purify the contaminated karma giving rise to that phenomena.  Here we are meditating on the emptiness of our samsara.  In particular, by meditating on the emptiness of our very subtle mind, it functions to purify our very subtle mind of all karmic obstructions.  When our mind is completely purified of the two obstructions, we become a Buddha.
3. My samsara is itself the nature of my biggest delusion.  The world our mind projects is the nature of our biggest delusion.  For example, a mind of attachment will project a world filled with objects of attachment that are beyond your reach and never provide any satisfaction.  A mind of anger will project a world of people in constant conflict inflicting harm on others.  A mind of ignorance will project a world pervaded by darkness, confusion and mistaken actions.  A mind of jealousy will project a world without any good qualities, or at least none within our reach.  A mind of doubt projects a world of great uncertainty and feelings of helplessness. 
4. I am now dying.  I am leaving behind my contaminated life created by my biggest delusion, and I am going to take rebirth as the guru deity who has the specific power to help all beings overcome this delusion in their mind.   We should strongly believe that we are now actually going to die.  The stronger we believe this, the more qualified will be our practice and our preparation for the real moment of our death.  The self that has this specific delusion is now going to be left behind.  We are now going to take rebirth as the guru deity who has the specific power to help living beings overcome this delusion.  This is the essence of tantric renunciation and bodhichitta.  Samsara can be understood as uncontrolledly identifying with the contaminated aggregates of samsaric beings.  Our “I” is uncontrolledly projected onto contaminated aggregates which suffer from birth, aging, sickness and death.  We see how the pure aggregates of the guru deity are so much better than the contaminated aggregates of our ordinary self.  Geshe-la said that if we die with a mind of compassion it is definite we will take rebirth in a pure land.  So we consider how if we are to be able to help living beings, we must take rebirth into the pure aggregates of the guru deity.  With this compassionate intention, we should strongly believe our old self has now completely died.  The appearances of our former life will never arise again.  There is no turning back, there is only going forward, rebuilding out of the clear light our pure land.  By training in this way, we create powerful potentialies to be able to practice in exactly the same thing at the time of our death, and in this way you take rebirth in a pure land.
5. I am the truth body of the guru deity.  We should Recognize this clear light as the truth body of the guru deity.  The Truth Body is the definitive guru deity.  He is the ultimate nature of all phenomena from which everything arises.  We should generate the divine pride of being Truth Body of the guru deity.   When we die, we want to die with our mind mixed with the Dharmakaya.  We train in life so that we can do this at the time of our death.  If we do, we will definitely be reborn in the pure land.  Geshe-la guarantees it!