Brief, intense, and infrequent!
Just remember there is no secret to building bigger, stronger muscles... it should be quite obvious that it's a lot of hard work mixed with intelligent planning and some common sense. You stimulate growth in the gym but you don't actually grow until your done in the gym, so make sure to allow for adequate rest and recovery not to mention overcompensation. If you have the same strength every time you enter the gym or you're getting weaker, it's not because your body is necessarily inferior, it just means you haven't given it enough rest to overcompensate from the exhaustive effects of an intensely stimulating strength workout.
Klosey is correct, you should never train like Arnold (3 hours a day, 6 days a week) because Arnold never should have worked out that much. The only reason he could get away with training that much is because of his "superhuman-like" genetics that allowed him to recover and overcompensate faster than the average human being.
For any of you noobies, you need to know (because some of you are ill-informed) ALL Mr. Olympia pro bodybuilders are on atleast 2 of the following 3 drugs: testosterone (steroids), human growth hormone (HGH), and usually stack with insulin. These drugs increase protein synthesis at an intense speed which allows the body to recover from workouts faster and build new muscle tissue at an alarming rate. These "Mr. Olympias" are no longer true bodybuilders, they are science experiments.
Do not get discouraged because your arms aren't breaking the 18, 17, 16, or even 15" mark. Majority of the pros lie about their arm measurements anyway and the others measure their arms pumped which you're not supposed to do and can add up to 1" 1/2 to their normal arm size. Arnold's arms were actually just slightly over 19" cold and they were the biggest of his time yet he states in pumping iron that they are over 23"!!!!!!!
One last thing, a muscular 15" or 16" arm is far more impressive than a bloated or puffy 17" arm. Trust me your arms will look bigger than they are if they are muscular.
Goodluck to any beginners and remember, bodybuilding is not a fad it's a lifestyle. Stay healthy my friends!