Serious question because I'd like another source, but what site are you using for info?
I'm using multiple sources... Rankings, profiles, mocks, etc.
WalterFootball.com: 2014 NFL Draft Prospect Rankings
NFL Draft - 2014 NFL Draft Prospects - CBSSports.com - NFLDraftScout.com
NFL Draft results, report cards, rumors and more | Bleacher Report
If I haven't watched them play before, then I follow these guidelines more or less:
Things I look for:
1. big board for prospect assurance
2. where analysts have them mocked (also look at writeups if available)
3. then I look at their profiles (pro's, con's, size, etc)