Practice makes perfect. But finding good data sets to practice with can be a pain. Here my current list for best places to find practice data sets:

• Toward Datascience: All the data sets you need
• Tableau: Free public data sets
• Kaggel (of course): data set library
• FiveThirtyEight: data sets
• Amazon AWS data sets
• Google data sets
• Wikipedia database downloads
• UCI machine learning depository
• CodeCrucks