I would target a woman living a good life. She would be middle-aged, possibly recently pensioned off from her business, wealthy, a secure person who has experienced good fortune. I would wear tight clothing. I would break into her house, then I'd wait until she found me. I would carry a short knife. I would injure her so badly that she wouldn't be able to run, scream or escape. Then I would put her body into the trunk of my car, and I would take her to the scene of the murder I was planning. I would wait till she had regained consciousness, at which point I would reassure her that I only want to rape her.
After this, I would have an air-tight coffin, into which I would place her. The coffin would be soundtight, and it would be aerated. Once she was in there, I would close off all the air holes, and she would steadily suffocate.
I might rape her if I got excited from this, but I probably wouldn't be capable of expressing my emotions strongly enough at the time to rape her.