As an American Christian who supports the call to BDS, I listen to the news and hear about companies who benefit from the Occupation Israel carries out in Palestine or support it and I choose to not buy products these companies make. And I generally choose not to buy anything made in Israel because Israel is an Apartheid nation.
As for the academic boycott, it is more difficult to practically see ways I can support it. I have to keep my eyes and ears open and watch for ways to support it.
But there are some things I have definitely learned from it , there is widespread discrimination against Israeli Jews and Palestinians in Israeli educational institutions. These institutions, through scientific develipments, are involved in making weapons used against Palestinians in the Occupation. And we all know Israel unlawfully targets civilians and commits many other violations of intl law in the Occupation. And last, many schools are built on lands stolen from Palestinians, schools sit on ethnically cleansed lands.
ALL of the above are reasons to support an academic boycott of Israeli educational institutions.