Hey Donyae – pps is plates per side.
The warm up honestly is all very relative and it comes to learning your body but basic rule of thumb should be as your load increases (prior to actual working set(s)) then your reps should decrease. I dont like to make big jumps in weight without allowing my body to acclimate to that load first. I find that touch several loads prior to my working set allows my nervous system to be truly ready to go although my muscular system might already be ready prior to. Something to think about is when you un rack a weight lets say on bench press or squat and it shocks you chances are your nervous system was not fully ready to handle that load so I would hit a few more warm up sets working up in load.
