Don't get suckered in to the "one size fits all" approach.
There are an untold number of sources you can find with advice about fitness and exercise. And that's good. Bodies are different and goals are different which makes the "one size fits all" approach a hindrance.
Between the dozens of health and fitness magazines and the nearly infinite number of websites and blogs, there are many thousands of people willing to share their experiences and knowledge. And that isn't a bad thing. I've learned quite a lot from different websites and blogs. What you should be wary of is absolutism, when people give advice that they claim is the one true answer. Many times, you'll find articles where one expert or another is supposedly debunking common myths about fitness and training. Frequently, when I read articles like this, they are just exchanging one myth for another.
For example, one of the “one size fits all” myths that is most commonly discussed is that long stretches of cardio exercise are the best way to lose body fat. Almost all the articles that describe this as a myth go on to state that interval training is vastly superior to steady state cardio. They'll give a basic interval training plan, like 20 seconds of high intensity followed by 90 seconds of low intensity and repeat. The article will say this one program they suggest will be far superior to basic steady state cardio and you should do only this one program to be most efficient with your gym time. While interval training is, for the most part, superior to steady state cardio, using only one plan for your interval training will eventually be treated by your body the same as steady state cardio.
There is a training concept called Specific Adaptation To Imposed Demands (SAID). The concept is that whatever you do on a regular basis, your body will adapt to it and it will become easier. Without SAID, no one would ever be able to run a marathon, as the body would never adapt to the longer distances. The SAID concept is also relevant when discussing interval training. If you continually feed your body the same interval training program, your body will adapt to it and each workout will become less effective than the previous one. To prevent this, you need a plan that incorporates several weekly interval cycles into an overall plan. Each week's program will be different than the week before and may include both interval AND steady state training. This way, your body does not adapt to the workload and your workouts will remain fresh to your body and nervous system.
The SAID principle applies equally to questions such as “should I use machines or free weights”, “how many reps should I do in each set” or “should I lift slowly or quickly”. The answer to all these questions is “What is your goal and in what phase of training are you?” There is no one answer for all the possibilities, even for a basic workout regimen. There always needs to be change, planned effectively, to maximize your efforts at the gym.
So any time you read an article that claims to have the ONE answer that will solve all your fitness problems, think to yourself “Yes, but what about next week?”