The Bible has much to say about our thoughts. In this study, we will be limiting ourselves to the word "meditation" and its verb forms, which are found in the Old Testament. Of course, there are many other passages - in both Old and New Testaments - that use other words to describe similar ideas. You are welcome to expand this study to include them.
"Meditation" emphasizes the things we silently think about, or mention to ourselves - things we reflect upon throughout the day. It can include those thoughts we would normally not share with others - even evil thoughts (NOT the focus of this study!). In some instances, it could include the communication of one's thoughts to others: the expressions (meditations) of one's heart.
The concept of "meditating," as used in the Bible, has little or no similarity with the concept of "meditating" that is common in certain man-made religions. In fact, with many of these, the idea of "meditating" would be more the opposite of what the Bible teaches, for they often encourage a person to NOT think - to "turn off" his mind or to focus on "nothing" or on some meaningless sound or phrase! Their goal is to "clear" one's mind from thinking! The Bible, in contrast, teaches us "turn on" our minds, and to focus them on God and what he has done.
Of course, this focus on God does not exclude thinking about other things in life. Everything that is good can have a place in our thinking. But remember, when we put God in first place in our lives and want to do everything in a way that pleases him, he has a part in ALL that we do!