It is wise to choose well what we are contemplating upon. We can also think deeply on a subject and that is deep contemplation. In contrast to meditation which is stilling the thoughts and through this stillness becoming aware of the unity of all things, contemplation is the act of focusing on a particular idea and becoming one with it and using this idea as a vehicle for understanding. Reading spiritual/religious texts, taking in nature, listening to music are all acts of contemplation. You can pick a piece of text from a spiritual book and work with it over a period of time using the text as a guide to looking at the world.