Good images of swimsuit models are planned and carefully created - they don't just happen because a photographer meets a model on the beach. The first step is defining objectives and finding a suitable location and model. Professional models are relatively easy to obtain and are the best starting point if you have the budget. They are experienced, and they know how to prepare themselves and what is expected of them. They also likely to have a range of outfits and an even skin colour. Those who are accustomed to working in warm or tropical climates will probably also have a great tan.
If you cannot afford a professional model then try contacting aspiring models, model agencies and schools, or even the local arts college. The selection of a suitable model is critical - get it wrong and you have failed before you start. This is just one of the reasons why a professional model makes things easier. The model will be selected by an experienced eye at the agency to fit your requirements. A good swimsuit model should obviously look good in a swimsuit, so make sure you see her dressed that way before you hire her. She should also have an attractive face, a good slim figure and long shapely legs. Good complexion, hairstyle and make-up are also essential. Of course it helps if she is also beautiful or drop-dead gorgeous!
Approaching young women with a view to photographing them in a bikini, perhaps less, must obviously be done carefully. The beautiful girl you spotted at the local swimming pool may be ideal in your eyes, but may have no interest whatever in your photography project. Start enquiring among friends and people who at least know who you are. Be completely open about your motives and never conceal anything. After all, if you cannot explain what you are doing, and why, there ma be something not quite right. Give any potential models a business card and leave them to make contact if they are interested. Never ask a second time.
If someone makes contact with you then invite them to a neutral location, perhaps over a cup of coffee, and show them just a few of your images in a small portfolio or on a tablet computer. This helps to demonstrate that you are a serious photographer. At the same time, explain in a little more detail what you are hoping to achieve. Even if the model eventually refuses your offer, she will probably be flattered by being asked. Never use photography as a pretext for obtaining a date, and don't expect someone who agrees to work with you progress to lingerie, glamour or nude work. If that is your interest, declare it honestly at first meeting. Trust is central to many types of people photography. Don't work with underage models.
Plan photography sessions carefully and try to think of all possible eventualities. Think about the needs of the model, what equipment you need and how it will be transported. Go through the plans with the model, or at least email a copy to her or her agency, several days before the shoot. The model needs to know what is expected of her on the day, and if she is unsure about anything there is time for her to contact you and discuss the details.
Make sure your swimsuit model has a hair stylist and make-up artist on hand, or is at least well capable of preparing herself. Without professional preparation, make-up is more difficult to get right and unlikely to be appropriate for photographic work. Have a look through the outfits the model intends to wear. Make sure the outfits are clean, properly pressed and free of unsightly creases. Also check that the model has blemish-free footwear - probably new shoes. Check that the model has removed all her jewellery - necklaces and rings look out of place when worn with a swimsuit.
Keep promises made to a model. Pay her on completion of the shoot and follow up with prints or any other commitments made.