Manipulate tension to trigger new gains. Remember, hypertrophy is stimulated mostly by muscular tension. Muscles get the most tension where the resistance curve is at its peak in the concentric (lifting) point of a movement.
For dips, anchor a band with a heavy dumbbell at your feet. Placing the band around your neck looks awkward, but it will naturally bend you forward and cause the pecs to get into a deep stretch. This will also create more tension at the top of the rep.
Unfortunately, your old "what do ya wanna work today?" spur of the moment type training works a whole lot better than anything the Soviet Ministry Of Sport managed to cook up behind the Iron Curtain back in the 50's and 60's. Charles Staley explains why.