When you are looking for a modeling agency make sure your consider print modeling. If you are petite and looking for a modeling agency. My first advice would be to focus on print modeling and print modeling agencies. Usually there is a modeling agency in your town, and to find it you can Google your city and then the words modeling agency or print modeling, or modeling, and you should see some agencies pop up.
Now to intrigue them despite being petite you can do two things:
1. Try to get photos that show you modeling products, handbags, shoes, showing smiles, and looking like an ad ( to get inspired look in magazines), also submit photos that do not stress your height but more your face, energy, personality and what you DO have. Then submit your photos 4x6 or 5x7 inches is fine or put together a nice comp card with your images from www.compcard.com Then include a letter and stress not that you just want to model, but also stress what you would be good at modeling and what you WANT to model, and why you would be a good model.
2. It might sound backwards but it does work- It is also nice if you can get some exposure as a model before you go to an agency 9 to show you can book work) for example, by submitting your photos to a local magazine or by browsing the ads in a local newspaper and contacting the companies and brands that might need models, such as hair salons, etc. If you can book work before you submit to an agency it will intrigue the agency more because you are showing them you can work as a model, you have worked as a model and they will be more likely to look past your height.
Stick to print agencies, agencies that submit to modeling work that involves print ads or commercials.