Don't crash yourself out, turn damage off and spin out your teammate
Maybe spin out some other cars as well, so your rival team finishes in 2nd/3rd positions. You get 25 points for the win, your teammate gets none, the other team gets 33 points, so you'll still lead the driver's championship but the other team will get closer and eventually take the lead in the constructors championship.
Sounds like cheating, I know, but is the most guaranteed way of doing it.
I remember doing this when I was at Williams, I didn't have to spin out my teammate since he never scored any points, but I'd always spin out other cars so the 2 McLaren drivers would finish in 2nd/3rd positions.