Hello Sissie
My first JY holiday was last year and I jumped right in and chose New Zealand as this is a place I had always wanted to visit. Like you and all other JY newbies I was apprehensive. Had a whale of a time and booked another holiday immediately on my return - Prague Vienna & Budapest. Went to Iceland for New Year and off to Norway in June. Have booked South Africa & Victoria Falls add on for March 2012.
So my advice to you is think about a country you have always wanted to visit and just jump straight in. You will not regret it. As for Prague, it was nice to visit but the hotel/food with my trip was just basic and adequate with smoking allowed in the bar. I have decided that I am not really into city breaks and prefer scenery.
Whatever you decide, overcome the nerves and enjoy.
Sylvia