Haven't exercised in a while or been a long time out of routine?
To get the muscles back into a great place to build form, go for high reps - as many as 30 for each muscle group. It seems tedious but you'll be laying down a great base to sculpt, build and develop from. Try this for two weeks. You'll be pleased you have.
Skipping this phase is like not tying your new shrubs up for a heavy winter snow, the branches will snap with the strain and be in trouble next season.