Strength
Fewer reps against more load, on the movements that carry over to everything else.
Nothing but the floor, a wall and a sturdy chair.
Three days a week, never two days in a row.
Rest two to three minutes between heavy sets so each one is done well. Keep two or three reps in reserve; no set here is a test of your maximum.
When you complete every set at the top of the range, add the smallest weight step or move to the harder version.
These routines are written for healthy adults. With an injury, a pregnancy or a medical condition, see a doctor or physiotherapist before you start.