This is a difficult question to answer. Only you the client can truly answer this question for yourself. In a perfect world, everyone would have access to an attorney whenever a legal question arises. Perhaps the best answer is that most legal matters should be handled by an attorney.
One of the most sacred of all legal principles is the attorney/client confidentiality privilege. In most cases this privilege is absolute and can only be broken by court order. Such court orders are very rare.
Yes, in personal injury cases the consultations are without costs. In criminal defense or family law matters, the initial consultation involves a reduced reasonable initial consultation fee.
When in doubt, provide your attorney with any and all relevant material to your case. If you are not sure, ask your lawyer if he needs certain written information. In personal injury cases we need accident reports, medical records and anything related to the accident. In criminal defense matters, the arrest report, and any paperwork related to the arrest is essential, including traffic citations where applicable. In divorce and family related cases, most financial records of the marriage will be important to access.