Dont exhaust yourself before you actually get to your heavy/strengthening sets.
the way I do it:
about 30% of heavy set 10 reps slowly, and then 10 quickly. ( put blood into muscles)
add 20 % 4 reps(adaption for tendons)
add 20 % 3 reps("")
add 10 % 2 reps("")
add 10% 1 rep("") After all this your muscles should NOT feel fatigued, but ready to go.
add 10 % do heavy sets.(makes you strong)
I added 15 pounds to my bench when I started this warmup. If any of you try it, tell me your results.