I have used many different drills, but this one always worked best for me. I have to do as many "good" pushups in 2 minutes as I can. 72 in 2 minutes is a maximum score in that event (army PT test) for my age group (I'm over 40)
Start with sets of 25,20,15,10,5 with one minute rest. This may be easy for you, it makes me extremely sore. Since this all adds up to 75 reps, & that's my target, Ill actually add more reps, so I'm doing more 100, in order to "trick" my body (or my head) into making 75 attainable in a single effort.
it's easier for me to add to the first set than add to the rest. I can generally work up to 40 fairly easily without stopping, so I make that the stopping point for the first set.
When you can succesfully complete the above sets, the progression continues as follows:
30,20,15,10,5
35,20,10,10,5
40,20,15,10,5
40,25,15,10,5
40,30,15,10,5
40,30,20,10
If that's not enough for you, at this point start taking 5 seconds off each rest period till you either get to a predetermined stopping point (20-30sec) or till you are whipping out 75 at once. Once I get to the last progression, even at 1 minute rest, I can always get close to 70 on a single effort.
I've always been amazed how much my lats are affected when doing these, as well.
As always, form is paramount. Upper arms should come down to parallel, body on line from head to heel. Head bobbing is discouraged, (OK, no juicy comments)
Hand placement is a important, just like on a bench press. Hands under shoulders, elbows in, uses more delt & tricep. wide hands, elbows out, more pec. Your body structure & strength level will determine what works best for you.
Good luck.
Longarms,
Former Chief Instructor,
95th Div Drill Sergeant School