One of the best and most concrete means of motivation is documentation. Start out with your weight and measurements on paper or saved in a document. Make sure you have the date, maybe even a picture. Measure your upper arms, lower arms, chest and thighs and document.
Each workout – document each exercise done, how much weight, how many reps and how much you had to push it.
At first it might seem pointless, but the reward will be when you have been working at it for a period of time and then look back on how much weight you have increased, how much more you can do and much different you look. It will keep you motivated, and motivate you more. If you are having a stretch where you think you are not getting anywhere there is a reference to measure with. It will help you evaluate your progress.
How you document your progress is not as important as doing it. You can make notes after each workout and date them, or you can use a program to keep track such as one of the Office templates. If you have Microsoft Office, there are some downloads you can find that will put your information into graphs and tables so that you can visualize your progress even clearer. Here, you will find downloadable templates that you can use for handwritten logs, computer logs or whatever your preference is.
There are some great apps to download for your phone that track your workout and even your nutrition.
my fitness pal is available for iPhone, android, Blackberry, or Windows
gym buddy is available in iTunes for iPhone