Known for its relentless touring schedule, let's-get-quirked-up songwriting and uproarious onstage patter, Guster knows how to give concertgoers their money's worth. The Boston trio met as Tufts University students in the early '90s, drawing crowds with a challenging anti-rock recipe: Take two acoustic guitarists, add a guy on bongos and try not to make it boring. Without help from a record label, the band sold 40,000 copies of its first two CDs, a feat that, predictably, got Guster signed to a major. Though the move didn't transform the threesome into a household name, it gave fans of Counting Crows and Dave Matthews a group that wouldn't embarrass them in front of their too-cool-for-that friends. With their first album in four years on the way, these still-young stage vets prove that the Boston market has more on its plate than stale Aerosmith leftovers.