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If you are flying larger aircraft, or intend to, take Dave Gwinn's course. Actually, I'd recommend his course over any others (like Archie Trammel, for example) regardless. You will know how to work the radar when you have finished his course:
www.davegwinn.com
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Agree, Dave is good. But I'd change your recommendation to "if you are going to fly radar equipped aitplanes, regardless of size".
Also, you need a good basic book on thunderstorm evaluation. None better than Dennis Newton's book. Taking a radar course without a solid foundation in thunderstorm meteorology is less than optimal. Dennis's book is very basic and understandable.
http://www.pilotsbooks.com/severe_weather_flying.htm