Meditation on the Five Aggregates of clinging
The five aggregates are
4) Volitional formations
The best way to study about these five is to read Khandasamyutta in the Connected Discourses of the Buddha. If you do not have a copy of the book then you may read a brief description from Bhikku Bodhi. Note that learning much about these five aggregates cannot be accomplished without reading the khandasamyutta and it may be one of the most greatest thing that you do to yourself by learning it.
The meditation on the five aggregates of clinging focuses on arising and passing away phenomena of 'form, feeling, perception, volitional formations and consciousness'. Buddha has explained the origin of form as follows
"One seeks delight in form, welcomes it, and remains holding to it. As a consequence of this, delight arises. Delight in form is clinging. With one's clinging as condition, existence; with existence as condition, birth, with birth as condition, aging-and-death, sorrow, lamentation, pain, displeasure, and despair come to be. Such is the origin of this whole mass of suffering."
The same thing is said about feeling, perception, volitional formations and consciousness.
Buddha has explained the passing away of form as follows
"One does not seek delight in form, does not welcome it, does not remain holding to it. As a consequence of this, delight in form ceases. With the cessation of delight comes cessation of clinging; with cessation of clinging, cessation of existence..... Such is the cessation of this whole mass of suffering."
The same thing is said about feeling, perception, volitional formations and consciousness. For further details see Samadhi Sutta
Volitional formations plays a significant part in our lives. In another discourse (in Khandhasamyutta), Buddha has said the following.
"The volitional formations construct the conditioned form as form, they construct conditioned feeling as feeling, they construct conditioned perception as perception; they construct conditioned volitional formations as volitional formations; they construct conditioned consciousness as consciousness."
Think what this means and use this when meditating on the Five Aggregates of clinging. In the meditation session, go through each part in details and observe the arising and passing away phenomena of form, feeling, perception, volitional formations and consciousness.