A good critique group will help you more than any other resource listed here. It is good to have members of varying gender, age, family background, career, and so on, because your potential readers will also be quite diverse. And if you can get people with backgrounds in medicine, law, and law enforcement, you have built-in subject matter experts for pretty much any question. Our critique group, the Really Cool Writing Group (RCWG) has been in continuous operation since 1995. The members have changed over the years and some, including me, have dropped out for periods and then rejoined. We have some guidelines for critiquing which have proved useful for us.