To gain mass, you must eat plenty of carbohydrates: 2-3g per pound of body weight. Carbs contain the calories required for growth, and glycogen to fuel intense lifting. Good options for most meals are brown rice, oatmeal, quinoa, and sweet potatoes. However, in your first meal of the day and your post-workout snack—when an insulin spike is needed to channel amino acids into muscles—you want fast-digesting carbs such as fruit, white potatoes, or white rice.
Walking into a gym to work-out for the first time can be intimidating, especially if you don't have proper guidance. Many new lifters either find themselves in that situation or are just training at home on some flimsy bench with a bar and a few plates. So, mistakes are common. Mistakes in terms of the exercises you're doing, how long you work out each day, how many days per week, the exercise form you're using, not to mention your eating habits.
Arnold wasn't just concerned with feeling the weight; he wanted to make sure the load induced muscle failure at a target range: "I make a point of never doing fewer than six repetitions per set with most movements," he notes," and nothing higher than 12. The rule applies to most body parts, including calves." Make sure to choose the right weight to fail within that rep range.
If a bodybuilder needed more recuperation time and could not recover adequately in order to train six days in a row, they could train more muscle groups in one workout. This would allow for more rest days so the body could recuperate better. For example, bodybuilders could train the chest, shoulders, triceps and calves on Monday and Thursday and their legs, back and biceps on Tuesday and Friday. By training all their muscle groups in a two day split instead of three, this would allow them three days of rest each week.

Warmups are important to get blood flowing to heart, lung, and muscles and lubricating (synovial) fluid loosening the joints ready for action. Each weights exercise should include a warmup with light weights and practicing the same form as for the workout weight. Sixty percent of your workout weight is about right for warmups. Stretching is not so important before exercise and is better performed after exercise. Some light stretches will do no harm.

The American College of Sports Medicine recommends that resistance training should be progressive in nature (for example, follow the principle of progressive overload - see below for an explanation), individualized, and provide a stimulus to all the major muscle groups (chest, back, shoulders, arms, abdominals, and legs). They recommend that beginners do one set of eight to 10 exercises for the major muscle groups, eight to 12 repetitions (reps) to fatigue, two to three days per week (multiple-set regimens may provide greater benefits if time allows). For older and more frail people (approximately 50-60 years of age and above), they suggest that 10-15 repetitions may be more appropriate.

Arnold frequently supersetted biceps and triceps movements—or, in other words, performed exercises back to back—to bring an enormous amount of blood into his arms. Blood carries oxygen and nutrients critical for growth, but these supersets also enabled Arnold to achieve his ultimate training goal: a killer pump. Supersetting a smaller muscle group like arms is easier than a larger one like legs, though Arnold often did that pre-contest as well.
The bulking and cutting strategy is effective because there is a well-established link between muscle hypertrophy and being in a state of positive energy balance.[19] A sustained period of caloric surplus will allow the athlete to gain more fat-free mass than they could otherwise gain under eucaloric conditions. Some gain in fat mass is expected, which athletes seek to oxidize in a cutting period while maintaining as much lean mass as possible.

Focus on those exercises, trust me, you won't regret it. Also, don't be afraid to add weight to the bar as well, as long as your form is in check. Overloading the muscles is essential for growth because the body doesn't need to adapt if nothing's changing. Therefore, you must force your body to change by adding weight or another repetition on that exercise that next time it comes around.
If someone is offering to spot you on an exercise (like the bench press), don’t assume they think you are a newb. Probably the opposite – they just want to help. If someone asks you to spot them and you’ve never spotted someone before, tell them that you would love to help but haven’t done it before so you could use some pointers. They will tell you what they want you to do.

BMR can also be estimated simply by multiplying body weight by 10-11 calories per pound or 22-24 kilocalories per kilogram. So, someone weighing 150 pounds has a BMR close to 1,500-1,650 calories per day. If you're pregnant, add 300 calories to your estimated calorie needs (don't take "eating for two" literally!). If you're breastfeeding, add 500 calories.
After session 12, consider whether you need to increase the weight for any particular exercise. If you can comfortably do more than the RM of 12 exercises, increase the weight by a modest amount, say two pounds or a kilogram for isolation exercise muscles such as triceps and biceps, and 5 pounds or 2.5.kilograms for compound and large muscle group exercises like squats and deadlifts. When using dumbbells, this would apply to each one. Don’t increase the number of sets beyond 3 at this time.