Help me pick a Lego set for my friends.
Lego has different sets for people in different ages. Each set usually has age guidance on the box. For small kids below 3 years old, I would recommend Duplo, because Duplo bricks have bigger size, and won't be swallowed by accident. For kids above 3 years old, but less than 10 years old, I would recommend Lego Classic. For those sets, people can use their imagination to create whatever things they like. For kids above 10 and adults, Lego Technic and Icons are super cool and good for display. 

For people interested in specific themes, like Star War, Harry Potter, etc, lego also has sets in those themes for you to choose from.