In theory, you want to look at a map and pick a spot that's sheltered from the wind and waves. In practice, I usually drive past my favorite spots and see how they look before I bother with that.
In my experience, the marine forecast is a lot more relevant than the humidity and UV index.
http://weather.noaa.gov/cgi-bin/fmt...Zone+Forecast<BR>Merrimack,+MA+to+Chatham,+MA
Also, you can get current conditions by calling NOAA Automated Weather Buoy 44013
http://www.ndbc.noaa.gov/station_page.php?station=44013
To access Dial-A-Buoy, dial (228) 688-1948 using any touch tone or cell phone. Assuming you know the identifier of the station whose report you need, enter 1. Then, enter the five-digit (or character) station identifier, followed by the # sign, in response to the prompt. The system will ask you to confirm that your entry was correct by pressing 1. After a few seconds, you will hear the latest buoy or C-MAN observation read via computer- generated voice.