I meet many guys who are considering becoming models. While I can't promise anyone that they will earn money modeling, I can help you position yourself in your best light and give you some pointers as well as help you prepare a solid portfolio of images.

I strongly recommend setting up a Model Mayhem account (no charge for basic level). You will need some nice photos to be accepted to the site. This is a good place to meet other photographers and models.

You will want to show a variety of looks and poses in your portfolio. Working with a wide variety of photographers can help you with this. Consider approaching photographers that do work that you like and see if they will work with you. Photographers are always seeking new and fresh faces.

Many models and photographers consider working for "TFP - time for prints". This means they are doing a shoot in exchange for prints (or images now that everything is digital). There is no exchange of money in this case. Both mutually benefit from the session without a direct expense. 

Spend time reviewing the portfolios of others to get ideas for poses and to identify photographers you may want to work wtih. Build a library of pose ideas and share them with photographers at your shoots. Spend time looking in the mirror or webcam (great idea to capture images of various looks you have). Practice posing your body and face. 

Be extremely professional and prompt in your interactions with everyone as people will share their experiences with others and you will develop a reputation over time. Consider carving our a niche for yourself - a look or type of work that you might like to be known for.

Show up to all appointments on time and ready to be actively involved in the shoot. Try different poses during the session (assuming the photographer is open to this) and bring props and outfits as appropriate for the session. Some of my best shots were from ideas that the model had and I always encourage everyone to just try things and see what might look good. 

As you develop more experience and a portfolio of images, you will then be in a better position to approach a modeling agency. Many work exclusively with a model and be careful of an company that promises too much and is really just looking for your money.