Builderman tips?

I right now try to main him but have a huge problems. Usually with targeting. How round goes: 1. I place buildings (sentry near looping spots and dispenser in safe spot, usually far from killer) 2. Do gens. 3. Killer destroys buildings. 4. I rebuild. 5. Killer started targeting me. 6. I die. How exactly should I place buildings to increase my chances to survive? Any tips?