Pesukei Dezimra, or "Verses of praise," are a group of prayers recited during Shacharis. They consist of various blessings, psalms, and sequences of other Torah verses. Two sources mention the obligation of saying Pesukei D'Zimra every day.
The first source is from the Gemara in Shabbos 118b, where Rav Yose says, "May my portion be among those that recite Hallel every day." The Gemara clarifies that he is referring to Pesukei D'Zimra.
The second source is from the Gemara in Berachos 32a, where Rav Simlai says that a person should always praise Hashem and only then daven.
Pesukei D'Zimra should be said slowly as if one is counting money (SA 51:8 MB).
The Levush writes (51:9) that one must be very careful to say it slowly because otherwise, it looks like you are trying to skip through your praise for Hashem to ask for your needs.
Kav Hayashar writes (Perek 34) that there are ten things for which one is judged in Shamayim, and one of them is if you say everything from Baruch She'amar until Yishtabach slowly and clearly.
When appropriately recited, Pesukei D'Zimra clears the pathways to Heaven so that one's Shemona Esrei will ascend smoothly to Hashem.