How to make my child bilingual?

I grew up trilingual. My parents would normally speak one language at home, but my older relatives would for most part talk to me in their native, minority language, and outside of family (school/friends) I would speak in English. it came out as something completely natural to me, and never made any confusion. Then in school and at university I studied other languages as foreign languages. What worked well for me was that each language related to a specific context, i.e. family vs friends or school, for example.