Street teams are groups of enthusiastic fans who help promote bands through grassroots marketing efforts like placing stickers and posters around their community, bringing friends to shows, encouraging music purchases, and requesting songs on the radio. Effective street team activities include placing promotional materials in public spaces, engaging with local venues and radio stations, and using online forums and social media to generate buzz among potential new fans. The document also discusses strategies for guerrilla marketing campaigns to promote news publications, including using QR codes, attention-grabbing graphics, and engaging target audiences on their preferred social media platforms.