Fitness for above 40 years of age
Always do stretching exercise after weight training and if possible also on off days.
Strictly keep proper form.
Take care of joints by warming them up and with proper form.
Initially do more repetitions per set.
Do exercises for rotator-cuff once or twice a week.
Start with multi joint exercises.
Take enough rest to recover.
Supplements to be taken after your proper diet is in place.
If possible have Personal Trainer of your age group who understands the nitty-gritty that comes with age and experience.
Take special care of Shoulder joints specially while doing bench press and military press.
Take care of knee joints with proper form, alignment, warm-up while doing squat.