Question: how many reps and sets for warm up?
Answer: The most common and effective warm-ups tend to increase weights while decreasing repetitions—e.g. 1 set of 5 reps; 1 set of 3; 1 x 2; and 1 x 1 each of these at evenly increased jumps in weight (more or less). For ease of loading, round up or down to the nearest five pounds where you can.