When my husband and I sent for our Y-DNA Kits from Ancestry.com and Family Tree DNA, we knew we had to choose DNA groups to join.
My Y-DNA kit was to be taken by my brother so that we could find out about our McGinnis male ancestors, while my husband's was for himself for his Massey male lineage.
So what groups should we join? The obvious choice seemed to be a surname group - McGinnis for me, Massey for my husband. But the Surname Project for McGinnis on FamilyTreeDNA only had 22 members and the description stated it was for "McGinnis from No. Ireland (Ulster)who settled in America. This project was started by testing two men whose ancestors came from Ulster to Eastern Pennsylvania before the Revolutionary War .."
That didn't fit what I wanted. My McGinnis ancestors were Catholics from Northern Ireland but they settled in Canada during the Famine Years (1840s). So after some thought and further research into what was available, I opted to join Ireland Heritage My McGinnis surname was listed, and the group numbers were high. I felt there was more chance of a match with others who were related in this group.
My husband wanted to join the Massey Surname Group on Ancestry.com but it only had one member. His decision was to join the Ireland Scotland Wales England British Isles Group which had 121 members.
We honestly had no idea how to make our choices, DNA testing was new to us both so we just decided that a criteria would be the numbers in the group, the geographic location the group was focused on had to match our known ancestral origins, and if possible, our surnames would be included in the group list.
So - our Groups were chosen, we had sent in our DNA sample kits and now we had time to do more reading in our struggle to understand what we would see when our results arrived.