Knowing which exercises to do and when to do them can be one of the most difficult things when beginning a fitness routine. One of the key points is to know the difference between a push and pull movements, as well as compound and single joint movements.
Any movement where you bring weight or force towards your body (e.g.: seated cable row).
Any movement where you bring weight or force away from your body (e.g.: pushup).
Movements that use multiple joints and muscle groups (e.g.: squats).
Movements that only one joint and muscle group is being used (e.g.: bicep curl).
Once you have figured out which movements fall into each category, you will now have to decide your training split based on how many days you would like to work out in a week. Of course, your routine will vary based on many things, such as goals, past/current exercise routines, fitness levels, etc.
A simple split that is great for beginners right up to the advanced gym go-er could be:
Day 1 – Chest/Biceps/Triceps
Day 2 – Quads/Hamstrings/Glutes/Calves
Day 3 – Back/Shoulders/Abs
Day 4 – Rest day
My personal preference is to always start with compound exercises, as they require the most amount of energy to do the movement. Then add in single-joint movements to fatigue muscles at the end of the workout.
An example for a Day 1 routine, after warming up, would be to start with bench press. After that, you could continue with compound push movements; adding pushups, dumbbell and/or cable flies. Once finished the compound movements, it’s time to go on to single joint exercises. Pick 4-6 exercises based on your level of fatigue and fitness. Movement examples for your arms are barbell bicep curls paired with triceps bench dips, alternating bicep curls paired with triceps kick backs and cable straight bar curl with laying down skull crushers.
Just remember: different bodies react to different routines. Experiment to find out which works best for you. Always listen to your body while getting enough rest and adequate nutrition.