Usually Amazon, but I go to independent record stores mostly, and if the price is the same or a couple dollars more, I'll purchase from the record store.
I usually buy singles on iTunes, and I stream sometimes on Spotify (its come to the point where I feel guilty when I use Spotify now)
mostly iTunes but only from a select few artists. I only buy physicals from Bey now just for my collection.
If I like the artist and the song but not enough to buy it, i'll stream it on Spotify
If I despise the artist but like the song, I'll get it illegally from several of my go-to websites.
I buy physical copies from my faves and albums that I really loved.
The rest of my music I stream. I used to buy my music on iTunes but like a month ago I got a pop up that my credit card info was changed and to confirm the changes and i freaked the **** out because i didn't change it. Now I don't buy music on iTunes anymore. Need to find a new way.