Who should be prepared to attend the first meeting with the estate lawyer? If the decedent had a Last Will and Testament, then the beneficiaries and Personal Representative named in the will should plan to attend in person or at least by telephone. If the decedent didn't have a Last Will and Testament, then the heirs at law should plan to attend. If you're not sure who the heirs at law are, the estate lawyer will be able to tell you once the lawyer understands the decedent's family tree, so the presumed heirs at law should plan to attend.
Of course, not everyone is open about their estate plan and many people will leave piles of documents that will need to be sorted through. If this is the case, then the family will need to work closely with the estate lawyer to figure out what the decedent owned and owed. Aside from this, if the decedent didn't leave a Last Will and Testament, then, as mentioned above, the estate lawyer will need to figure out who is entitled to receive the decedent's property after understanding the decedent's family tree.
Probate Checklist - 8 Steps to Opening a Probate Estate