Focus on form. Good form means you can reap all of the benefits of your workout and avoid injuries at the same time. To maintain proper form, pay attention to your posture (stand tall with chest lifted and abs held tight), move slowly (this ensures you're relying on muscles, not momentum, to do the lifting), and remember to breathe. Many people hold their breath while exerting, but exhaling during the hardest part of the exercise helps fuel the movement.
Design your training regimen to conform to your athletic objectives. Many athletes cycle their training according to their competition schedule. Three to four months out from a fight, a boxer might "train heavy" for strength and power. By eight weeks out, he/she has decreased the weight, increased his reps, and cut back on free weights to emphasize cables and machines. During the last four weeks, he/she eliminates weight-training altogether, concentrating entirely on speed drills and boxing. A power lifter will employ the opposite strategy. Three months out from a meet, he/she may incorporate many different exercises into his/her routine including machines, cables, and free weights. Two months out, the reps have dropped and so have the number of different exercises. The last weeks before the meet may include sets of only two or three reps of the most basic movements: bench press, squat, and dead lift.
Patience is something almost every beginner lacks, but is also a vital key to success. When first stepping in the gym, progress may come rather quickly, whether it is in the form of size or strength gains. Depending on your body, your progress will begin to decrease after a period of time and adding weight to the bar will become progressively difficult.
At the end of the day, you have to focus on how you feel. “Listen to your body,” says Davis. “It tells you when it needs a day off.” As a rule of thumb, take a rest day if your perceived pain is above a seven on a scale of 10, Davis advises. Or, focus on a different body part (say, if your legs are sore, focus on upper-body moves). Can't stop, won't stop—at least, till your next rest day.
If you decide to join a gym, know that you're not expected to know how all of the equipment works right off the bat—or what to do with it. Be sure to take advantage of the free orientation so you can learn how to properly use everything that's offered and set up a basic strength-training program. At the gym, machines are preferred for beginners, because they're quite safe: Most require little coordination and offer more stability than free weights while performing the movements. 
So, for example, with the moves above you'd do 15 squats followed by 15 push-ups. Take a little breather then repeat that two more times. Then you move on to your walking lunges and lat pull-downs (and repeat those three times total, too). You can really do anywhere from eight reps to 15 (and even just two sets, if you don't have time for three), but "it’s not a bad idea for beginners to start with a 15-rep range to get comfortable with the exercises," says Davis. And while there's some debate over whether three sets of an exercise is really best, "it’s a great beginner model," says Davis. Don't overcomplicate things when you're just getting started.
The motor proteins actin and myosin generate the forces exerted by contracting muscles. Current recommendations suggest that bodybuilders should consume 25–30% of protein per total calorie intake to further their goal of maintaining and improving their body composition.[30] This is a widely debated topic, with many arguing that 1 gram of protein per pound of body weight per day is ideal, some suggesting that less is sufficient, while others recommending 1.5, 2, or more.[31] It is believed that protein needs to be consumed frequently throughout the day, especially during/after a workout, and before sleep.[32] There is also some debate concerning the best type of protein to take. Chicken, turkey, beef, pork, fish, eggs and dairy foods are high in protein, as are some nuts, seeds, beans, and lentils. Casein or whey are often used to supplement the diet with additional protein. Whey protein is the type of protein contained in many popular brands of protein supplements and is preferred by many bodybuilders because of its high Biological Value (BV) and quick absorption rates. Whey protein also has a bigger effect than casein on insulin levels, triggering about double the amount of insulin release.[33] That effect is somewhat overcome by combining casein and whey. Bodybuilders are usually thought to require protein with a higher BV than that of soy, which is additionally avoided due to its claimed estrogenic properties. Still, some nutrition experts believe that soy, flax seeds and many other plants that contain the weak estrogen-like compounds or phytoestrogens, can be used beneficially, as phytoestrogens compete with estrogens for receptor sites in the male body and can block its actions. This can also include some inhibition of pituitary functions while stimulating the P450 system (the system that eliminates hormones, drugs and metabolic waste product from the body) in the liver to more actively process and excrete excess estrogen.[34][35] Cortisol decreases amino acid uptake by muscle, and inhibits protein synthesis.[36]
Where you go from here is up to you. With 25% more strength, you’re no doubt carrying more muscle. Maybe it’s time to step into a cutting cycle after a week or two off. Or, if you feel like this methodology set you on the path to even greater gains, you can always start the program over, perhaps aiming to add even more strength and size to your new physique.
An obvious one I know, but many misjudge this. If you have two weeks to get ready for the beach then the quickest way to drop fat (and subcutaneous water that can blur muscle definition) is to drop your daily carbohydrate intake to 50 grams of fibrous carbohydrates. So say hello to broccoli, cauliflower and kale, and kiss goodbye to breads, cereals, fruit, rice and pasta. Where people go badly wrong when dropping carbs is that they simply switch to eating lean proteins and don’t replace some of the lost carb calories with calories from fat. This inevitably leads to an energy crash and the subsequent blowing of the diet because the trainee simply runs out of steam and willpower. A few whole eggs, a piece of steak and plenty of supplemental Omega 3s (I prefer 10 grams a day for carbohydrate tolerant individuals, more if there appears to be insulin resistance) work wonders. 
Here is a very good bodybuilding workout routine tip you can use to determine the exact number of rest days between training sessions. Track your weight, and reps. If your strength continues to increase, you are resting between training sessions in an optimal manner. If the weight plateaus, or decreases, add additional muscle building rest days between workouts.