If you have just started weight training and you want to get fit while increasing the strength that you have then you should be training no more than three times a week. However if you have been training for more than a year then you should be training with slightly lower reps and a heavier weight.
The secret to gaining strength and fitness at the same time is the amount of time you spend resting between sets. The less time you rest between sets the more cardio you will be doing between sets as you start to feel the approach of failure no matter how strong or how fit you might be.
If we assume that you have never trained before then the following fitness routine will get you good results even if you only train it twice a week. The secret is to push yourself so that you are able to achieve the high intensity training that will get you the results that you are looking for.
The rest between sets should start off with around 90 seconds rest between sets. However as stated above the objective is to lessen the rest period between sets as you start to get stronger and fitter. The objective should be to first reduce the rest period between sets to around 30 seconds before you adding more weight.
The last point that needs to be added is doing correct form when doing any movement. If you are unsure what is the correct form for doing any of the movements listed below then you should ask someone who knows what they are doing. You should always do slow and controlled movements with no momentum and no bouncing.
Before you lift any weight a 5 or 10 minute warm-up is required which should be done doing light to moderate cardio work like walking fast on a treadmill or working with medium resistance on a stationary bike. There are many other alternatives for a good warm-up so you need to look around and see what works best for you.
Leg-press 3 sets of 8 to 12 reps
Leg extensions 3 sets of 8 to 12 reps
Lying leg curls 3 sets of 8 to 12 reps
Seated leg curl 3 sets of 8 to 12 reps
Wide grip pull-ups 3 sets 8 to 12 reps
Machine press 3 sets of 8 to 12 reps
Machine chest fly or pec deck 3 sets of 8 to 12 reps
Triceps pushdowns (rope) 3 sets of 8 to 12 reps
Machine biceps curls 3 sets of 8 to 12 reps
Machine shoulder press (military press) 3 sets of 8 to 12 reps