I prefer decline dumbbells myself to dips, just feel the dips too much in my tris. If you DO dip, I suggest you keep your head buried on your chest where you can actually FEEL the pecs contracting at the top, helps you focus much better...
I LOVE weighted dips too but my shoulder can't handle them right now. I was up to 75 lbs (plus my 218 lbs frame)for reps of 5. Maybe not a lot for some of you, but it was for my gym.