online sportsbook

What is the correct way to play within a sportsbook that changes from the standard -110/100 line? For instance, I was going to play the Carolina Panthers at -2.5 but the line listed was -3 and +102/100. The line for Seattle was -118/100. I have noticed this happening all year on various games and have decided not to play. Whereas, I was a winner more often than not (I only tracked the results on paper), I would have ended up losing in the long run.