Merely thinking about God and your divinely appointed purpose in the world is one of the most powerful exercises for centering yourself in God. Contemplating on the love of God, His infinity, His greatness and His compassion brings us closer to our Heavenly Father.
The Psalmist said, "I will meditate also of all thy work, and talk of thy doings." (Psalms 77:12) And the Apostle Paul added, "Finally, brethren, whatsoever things are true, whatsoever things [are] honest, whatsoever things [are] just, whatsoever things [are] pure, whatsoever things [are] lovely, whatsoever things [are] of good report; if [there be] any virtue, and if [there be] any praise, think on these things." (Philippians 4:8)
Moreover, the things you set your mind on will influence your entire being. Jesus said, "The light of the body is the eye: if therefore thine eye be single, thy whole body shall be full of light. But if thine eye be evil, thy whole body shall be full of darkness. If therefore the light that is in thee be darkness, how great [is] that darkness!" (Matthew 6:22-23)
When Jesus speaks of the eye, He means both the physical eye and the mind's eye. In regard to the physical eye, control what you look at. Visual images influence your thoughts. Don't watch garbage on TV. Turn your eyes away from tempting images. In regard to the mind's eye, don't visualize that which is sinful and ugly. Visualize those things you know Christ approves of.
Here is a contemplative exercise: Look at a flower, a tree, the sky, and think upon the One Who created these things. Look at your hands, at your face in the mirror, and realize that God created you. Remember the words of the Lord Jesus, "Are not two sparrows sold for a farthing? and one of them shall not fall on the ground without your Father. But the very hairs of your head are all numbered. Fear ye not therefore, ye are of more value than many sparrows." (Matthew 10:29-31) And then think this thought, "The God Who created the entire universe with all its galaxies and solar systems, knows me as an individual, and cares about me deeply. He is my Father and I am His child." These are powerful thoughts. They will lift you up and make you feel better.
But most importantly of all in your contemplative journey, read the Bible. It is God's Word written for God has given us His word that we may know Him. It is our map for finding God and pleasing Him. The Apostle Paul said, "And that from a child thou hast known the holy scriptures, which are able to make thee wise unto salvation through faith which is in Christ Jesus. All scripture [is] given by inspiration of God, and [is] profitable for doctrine, for reproof, for correction, for instruction in righteousness: That the man of God may be perfect, throughly furnished unto all good works." (II Timothy 3:15-17)
And share the Christian experience with fellow believers. Jesus said, "For where two or three are gathered in My name, there am I in the midst of them." (Matthew 18:20) And the Apostle Paul said this, "Wherefore comfort yourselves together, and edify one another, even as also ye do." (I Thessalonians 5:11)