I found a lot of information on this subject. I went through a lot of research material and condensed it down to the most important tips. I am quite familiar with these tips, as I’ve experienced the difficulties associated with them all. I’ve never hired a personal trainer, though.
This is a general guide that will go over the basic principles of a strength training program.
If you have any medical conditions, it is important to talk to your doctor before beginning any fitness program.
[Table of Contents]
–Warm Up/Cool Down
–Importance of Form and Technique
–How Much Weight to Lift?
–Set and Reps
–Training Frequency and Rest
Continue reading to learn more about the guidelines of a good strength training program.
When it comes to strength training, the question of what equipment to use may come up.
The good news is you do not need any equipment to train strength. Check out the article on body weight exercises to learn more about how to incorporate them into your strength training program.
If you do have equipment to use, great! Free weights and machines are most often used to strength train.
If you’re just starting out, dumbbells are a great and versatile piece of equipment for training just about any part of your body.
Whether you’re just starting out or have been training for a long time, it never hurts to consult a fitness professional.
Hiring a personal trainer can help you set up a workout plan or evaluate an existing one you already have. If you’re a complete beginner and have no idea how to even do any exercises, a personal trainer can show you how to do them.
You can hire a personal trainer at a gym or you can have them come to your home if you prefer to workout at home.
Warm Up/Cool Down
Many often neglect Warm-ups and Cool-downs, which are an important aspect of strength training. You shouldn’t skip these as they are very helpful in avoiding injuries.
The purpose of a Warm-up is to get the blood flowing in your muscles before working out. Basically it gets you ready for physical activity. Simple warm-up exercises include things like jogging or arm swings. Light cardio and exercises that will loosen you up around the joints (range of motion exercises) are great for warming up. A favorite warm-up of mine is to do the exercises I’m planning to do but with very light weight. This is a common way you’ll see people warm up before doing lifts like bench press or deadlifts. One of their warm-ups is doing the exercise with an empty bar. For best results, warm-up for 5-10 minutes. Do not rest between warm-up exercises. 
Make sure to also do a Cool-down at the end of the workout. Doing a Cool-down will help prevent dizziness/fainting and muscle cramps.  The idea here is to do slow movements to help you relax. Stretching is most often done at the end of the workout for this reason. Again, aim for 5-10 minutes before finishing. Do not rest between stretches.
Importance of Form and Technique
Having good form when weight lifting is essential to making progress in your fitness goals. Improper technique limits your progress and you will be more susceptible to injury. 
So the question is, what exactly is good form? That means no cheating and doing the exercise in a slow and controlled manner. To do slow and controlled, aim for 2 seconds on the way up, and 2 seconds on the way down.  Cheating is doing things like using momentum, not using a full range of motion, or incorporating other muscles to assist in the lift.
Before doing a new exercise, make sure you do your research on it to learn how to do it correctly. You can also ask a personal trainer or fitness coach on how to do exercises with proper form if you are unsure.
How Much Weight to Lift?
It’s best to start light, and work your way up. The best way to gauge this is if you can do 12-15 reps of an exercise in a single set.  The last rep should be difficult, but doable. If you can do an exercise for 12-15 reps with good form, then it’s safe to say you can increase the weight. Remember, it’s always better to go too light than too heavy.
Set and Reps
A good rule of thumb is to do 1-3 sets for 12-15 reps for each exercise.  As long as you are fatiguing your muscles, you can expect to see progress in strength gains and muscle size.
This is an important topic that should not go unmentioned. A lot of beginners may have the false notion that they must lift heavy weights. There seems to be an idea that if you lift light weights that you will be harshly judged or made fun of, but this is simply not true. There’s also this idea that you should never use light weights, which is also wrong.
It is important to challenge yourself every time you do a workout. This does not mean that you need to attempt lifts that you can barely do. Making this mistake will not only not impress anybody, but it will slow progress and likely lead to injury. Save the heaviest weight for the last set of your exercise and make sure you can do at least a few reps of it with good form.
Your fitness journey is yours alone. If you have to start with the lightest weights available, that’s okay. Everyone, including the most jacked guys in the gym, had to start somewhere. As long as you continue to show up and train, you will eventually be able to lift heavier weights.
Do not hold your breath when lifting weights. While it may feel natural to do so, holding your breath can actually lead to injury. (Hernias) 
The proper way to breathe when lifting weights is to exhale on the way up and inhale on the way down.  In other words, when you are doing the hardest part of the movement, breathe out. Similarly, when moving back to the starting position, breathe in. Repeat this breathing pattern for every rep. It may seem difficult at first, but eventually it becomes second nature.
Drinking enough water when doing any workout is crucial to performing at your best.
Not hydrating enough can lead to worse performance when training and you won’t recover as quickly. As a result, dehydration can lead to injury.  Hydrating also allows your body to more efficiently transport nutrients to your muscles.
Make sure to drink plenty of water before, during, and after your workout.
As you get stronger, you will find that the weight you’ve been using will become easier to lift. It is important to progressively increase how much you lift over time so that your muscles can continue to get bigger and stronger. This is called Progressive Overload.
“No pain, no gain” is a commonly heard phrase in the weight lifting world. And it’s true. The key here is knowing what is good pain and what is bad pain.
Feeling the burn as you do an exercise is good pain. This feeling is often gradually felt as you do the exercise. You will feel the pain spread out over the whole muscle you’re working. 
If you feel sharp pains or pains that come on very suddenly, that is bad pain. It is often very difficult to tolerate and often fixated in a certain area.
If you ever are experiencing bad pain, stop the exercise immediately. Ignoring bad pain can lead to more severe injury. If severe enough, you’ll be unable to train for a long period of time.
If you get injured while working out, see your doctor.
Training Frequency and Rest
Workout at least twice a week. Ideally, you want to train each major muscle group twice a week.  There are several common workout plans that allow for this, such as the Push-Pull-Legs split.
Do not skip training muscle groups! If you skip certain muscles in favor of others, this will lead to imbalances. Muscle imbalances are a one way ticket to getting injured. From an aesthetic point of view it will not look good either. This is why you may commonly hear jokes about skipping leg day.
Rest is just as important as training. Your muscles grow during rest periods. If you are constantly working the same muscles, they’ll never have the chance to grow. Make sure not to train the same muscle(s) twice in two days. Give at least a full day’s rest between workouts before hitting a certain muscle again. 
Fitness is a marathon, not a race. You can’t expect to see rapid gains in a short period of time. It takes at least 6-10 weeks to see noticeable gains. 
You have to be consistent. Consistency over a long period of time will allow you to see the gains you want. It’s all about perseverance.
Generally, it’s good to stick with one routine and be consistent with that. There are times when it can be good to change things up.
If you are finding yourself bored with a workout or find it too easy, change it up. If you do not see any progress that’s another good time to change things up a bit.
You can change your routine by including more sets or reps. You can also replace some exercises with others. Sometimes, you can even completely change your workout routines. Just don’t switch it up too much or you may slow your progress.
Strength training can be intimidating, but we all have to start somewhere.
To learn more, see the article on the benefits of weight training.