I got a pretty great imagination when it comes to that.
Usually, I don't jerk when watching porn, I'll watch it for fifteen minutes or so, and just get hard as fuck and play with my dick, stroke it a little, it's kinda like foreplay. Then I take it into the bathroom, turn the hot water on, get it wet, and finish it off.
Sometimes I'll jerk it while looking at sexy pictures of chicks, I like em not nude, but just barely clothed, like bikinis or underwear, or I'll look at pictures of chicks I actually know. Lol if they only knew, "Hey thanks for that FB album, Bahamas Summer 2013! I been really enjoying it!"
But, mostly, I like to use my imagination.
It's mostly chicks that I know or have known that I want to bang, and I'll come up with a scenario in my head and kind of watch it unfold. Maybe we're going skinny dipping, and they're staring at my big dick and one of em starts blowing me while the others watch, or we're all taking a shower together and I'm fucking one of them while she tells me how big I am. Maybe one's in a skintight Supergirl outfit and the other a leather Catwoman outfit and she's saying "Fuck me Superman!" Shit like that.
Or I'll go back in my memory bank to a sexy memory I have stored, a couple hot girls in Catholic school girl outfits talking about big dicks, and I'll let my imagination take over from there.
I haven't smoked weed in a couple years, but that's one thing I really miss about it. I used to have a ritual of getting super stoned, then turning on the hot water in the shower. Smoking weed just lights a fire to my imagination and makes it ten times more vivid, like I can actually picture the things as if I'm watching it on TV. I highly recommend, for anybody who hasn't tried it yet