I would recommend that you get the Property Guide - published by Sheffield Newspapers who also publish The Star.
Best areas are to the west side of the city - those which lead towards the Peak District. But, they're the most expensive ones too. However, Sheffield housing is cheap compared to, say, the south of England so you may be able to afford some good propeties.
Viewing the areas is essential - and ask the locals, we're a friendly bunch.
If you want to state specific areas, then post here.