I've been to Prague once. One thing that might be good there for a solo traveler is to take the walking tour of the city. I did this and had wonderful conversations with the guide --there were only about 6 of us on the tour. My guide was a young college student and such individuals may have helpful tips on things to do in and out of Prague.

Eating at pubs is a great idea, as is eating once or twice in the hotel (if you are staying at a hotel that has a restaurant). When I have traveled alone I try to find a restaurant or pub that is not packed; if I feel comfortable there I may go back--why not if the food is good, etc?

Prague is also a great place for concerts--all over the place and these can provide occasions that interrupt the sense of "aloneness" that sometimes creeps up.