Visualize - I now that this may seem a little strange to some of you but this is usually the top tip I give to people when asked how to get muscular. The simple reason is that if you don't have a definite picture in your mind on how you want to look then how can the mind communicate to your body what you want it to do? As soon as your mind has a clear vision of what you want to achieve then you will start to workout with a purpose you never knew possible and you begin to see results you never thought possible.
Diet - I am often shocked to see people drinking cans of fizzy pop and eating bags of potato chips after they have finished working out at the gym. While most people use appetite suppressants to control their diet, others are just so stubborn to avoid their wrong eating habit and the simple fact is that you can workout in the gym every day for the next 6 months and see very little results if you are eating the wrong foods. My advice if you are just starting out would be to start off slow and gradually start to cut junk food out of your diet. After a few weeks you will start to become more disciplined and the wrong type of foods won't even be an option anymore.
Recovery - If you workout too often then the chances of you ever getting the muscular body that you want is not very good. Your muscles need time to rest and recuperate so that they are able to properly repair themselves and grow back bigger. Another important aspect to this is to make sure that you get enough sleep, usually around 8 hours a night. Ensuring that you get a good nights sleep will mean that you will be refreshed enough to attack your workouts with the proper intensity.
As you can see some of the best tips on how to get muscular have nothing to do with the workouts themselves but the things you do away from the gym. Of course, the workouts are very important but if you look at the above steps then will see that building the foundation for those workouts is just as important.