1) Get inspired.
Look back on the times when you enjoyed being around her, discovered that you have a lot in common, or realised that you had tremendous respect for her.
2) Put yourself in her shoes.
Based on what you know about her, imagine what language or situations might make her uncomfortable, and avoid them. If you are unsure, err on the side of caution. Avoid overemphasizing the appeal of her physical appearance.
3) Choose an appropriate venture for your disclosure, so that you can avoid embarrassment and awkwardness. Take her sailing, and say it amidst the waters.
4) Make yourself clear.
You don't have to be cryptic to be tactful.
Rather than wrapping your feelings of romance in a riddle, clearly convey your attraction.
5) Keep the door open for a response, without putting pressure on her. Let her know that you want to remain friendly, even if you do not develop a closer relationship.
6) Give your declaration some time to sink in.
It may take a few days or even weeks. Once you start counting the months go by, you can safely bet she is not interested.