"Blessed" Beatification is a statement by the church that it is "worthy of belief" that the person is in heaven, having come to salvation. This step depends on whether the Venerable is a martyr or a "confessor".

For a martyr, the pope has only to make a declaration of martyrdom, a certification that the venerable gave his or her life voluntarily as a witness for the faith and/or in an act of heroic charity for others. This allows beatification, giving the venerable the new title "Blessed" (abbreviated "Bl.") or, in Latin, Beatus or Beata. A feast day will be designated, but its observance is normally restricted to the Blessed's home diocese, to certain locations associated with him or her, and/or to the churches or houses of the blessed's religious order, if they belonged to one. Parishes may not normally be named in honor of a Blessed.

If the Venerable was not a martyr - all non-martyrs are "confessors" as they "confessed" or bore witness to their faith by how they lived their lives - it must be proven that a miracle has taken place by his or her intercession - that is, that God has shown a sign that the person is enjoying the Beatific Vision by God performing a miracle in response to the Blessed's prayers. Today, these miracles are almost always miraculous cures, as these are the easiest to establish based on the Catholic Church's requirements for a "miracle." (The patient was sick, there was no known cure for the ailment, prayers were directed to the Venerable, the patient was cured, the cure was spontaneous, instantaneous, complete and lasting, and doctors cannot find any natural explanation.)

-- Canonization - Wikipedia Article

Since the Canon law reform of 1983, one miracle must be proven to have taken place through the intercession of the person to be beatified, though this requirement is waived for those who died a martyr. -- Beatification - Wikipedia

For more inforamtion on the process leading to beatification: The Process of Beatification in the Catholic Church