Ok the sum answer is: the counsel of his own will (Eph.1:11).
But that begs the question: what do you think the counsel of his own will is based on? Again, what is the criterion?
George, it is not begging the question when the question is asked of God. We know from scripture that God's thoughts are not our thoughts:
Isaiah 55:8-9 8“For My thoughts are not your thoughts,Nor are your ways My ways,” declares the LORD.9“For as the heavens are higher than the earth,So are My ways higher than your waysAnd My thoughts than your thoughts."
We read in Romans 9:
Romans 9:20-21 20 On the contrary, who are you, O man, who answers back to God? The thing molded will not say to the molder, “Why did you make me like this,” will it? 21 Or does not the potter have a right over the clay, to make from the same lump one vessel for honorable use and another for common use?
The short answer is that scripture does not reveal a criterion for whom God elects other than it glorifies Himself. Why did he elect you and not your next-door neighbor? Hopefully, no one will be so arrogant as to say, "He elected me because I chose Him", as though the thing molded has any influence over God in the matter.