Another important concept is Total Quality Time Management. As a rule of thumb for most types of training if you can perform the same routine in a shorter space of time it is good, it means your body can recover faster between exercises and your heart and lung power is improving. I always aim to complete a routine in as short a time as possible without speeding up the reps, ie. I aim to minimise breaks in exercise. This is something you should look to start doing after a couple of months of training.
You should tailer your routines to what you want to achieve, and change your routine everytime you do it otherwise you will stop making good gains. For example if your goal is general fitness you will probably concentrate more on cardiovascular exercises such as running, if you want to lose weight it is best to focus on both strength and fitness exercises and if your soal goal is to get stronger I would advise you focus more on bodyweight exercises.
When you enter a gym or train at home train I recommend you start with CV then stomach/back then legs and finish with upper body. And remember your breathing is very important, as a rule of thumb you should breath out while performing the hardest part of an exercise (eg. the pushing part of a bench press) and breach in while performing the easy part.
As a final note you should look at cross-training - there are many different types of exercise you can do, for example bodyweight exercises, running, cycling, swimming, etc. and many variants within each. Try to constantly change your workout and remember to listen to yourself, if you don't feel like running that day, don't, do something else.