Make a big splash with your first novel.
Not necessarily, but it's probably your best bet.
Until the mid 1960s, publishers had fairly modest expectations for sales of a first novel, but by the late '70s, they had lost patience.
The most successful authors in this group hit the ground running..Their first books set the pattern for their careers. Brooks's first novel in the "Shannara" series was a bestseller. He continued with the series, later starting other series, always in the same genre (fantasy). Jackson and Chesbro have continued to write about the detective heroes who debuted in their first novels.
A welcome exception to the rule is Townley. His first novel didn't do particularly well. More than 20 years later, he hit his stride.