Ask the testator herself, during her lifetime, whether you are an heir in her will. Realize, before asking, that a testator's will is private and personal while she is alive. She changes it at will, either by a codicil amending a bequest or else by a superseding will. She voids it by crossing out the terms of the will or ripping it up. The only legal manner of determining whether a living testator names you in her will is to ask her directly.
Ask the executor -- after the testator's death -- whether the will contains a bequest for you. An executor is the person charged with steering the last testament through the probate process. The court supervises the executor's management of the estate, initially determining whether the will is valid, then requiring and reviewing reports until distribution. An executor owes the highest possible legal duty, termed a fiduciary duty, to the heirs and must inform them expediently of their bequests. Call the executor and ask directly whether the testator named you an heir.
Locate the executor by locating the will. If you do not know the executor's identify, find the court that probates the will. Generally the court in the county in which the testator resided has probate jurisdiction. Visit the court clerk's office during business hours. Provide the name and date of death of the deceased and request the probate file. The probated will is among the early filings. The will usually names an executor and, when it doesn't, the court appoints one. Locate the name and address of the executor in the file and contact him or simply look in the will to make the determination yourself.