Find a professor...

This has accidentally happened to me more than once. Find a professor who's work you find really interesting. Read all or most of what they've published. Try to come up with 20 good questions. (It will turn out only four or five are good.) Find a time when they are not busy, such as their office-hours early in the semester for courses they are teaching. Ask them what they suggest reading next. Good chance they'll invite you to attend their seminars or suggest you apply for a position in their Phd program. Professors/researchers in their forties or older generally know that grades and recommendations only convey so much information. It's generally best to personally and directly interact with the most interesting and intelligent professors. They tend to form their own opinions about academic potential.