Use full range of motion.
Try pre-exhausting, etc. This is really all for nothing though, as for you to actually get some decent pec develpment you have to gain weight. I realize that you're not a powerlifter nor do you want to be, but the pursuit of strength is in line with your current goals.
I see a lot of people out there who tell me that they just want to look big, they don't care about strength... well... I've never seen a truly impressive physique on a guy who didn't have some substantial strength. Powerlifter levels? Not necessarily. Just strong. You know it when you see it. If you're incline pressing 185 for a couple of sets of 10 and you raise that to 275 or 315 for 10 reps... I promise you that you will look like a totally different person.
If that's not what you want to hear, then just try some variety some as pre-exhaustion, lots of flyes, etc. I think you'll find that you'll make small but noticable changes like that, for head turning changes you would need to do something more drastic. Remember, this is a marathon, not a sprint.