I guess theres 2 'styles' of masturbation for me.
1st, jacking off while surfing for porn....movies, pics, stories, chat etc. And to be honest i dont think i think about anything other than 'fuck thats hot, god i need to cum'
2nd, jacking with no visual stimulation... like when you knock one out in the shower or in bed at night etc. Thats where i think about stuff. i fantasize about women ive seen around. maybe from work, or from back in school, or just some random hottie ive seen. I tend to imagine myself as if i were actually there. Ill think about her undressing, what id do to her, how id do it etc. Its harder work thats for sure.