You ask a tough and good question! Which ranking si the best?? Actually there is no "best"... they work a bit differently, and to get a sense of how they do, you need to read their ranking criteria on their website. But you should know that in the US, US News is considered the "authority" while Bsuinessweek is the alternative... and the FT is the more useful one if you are looking for schools outside the US.
As for where to start, a good place to start is with schools which have an average GMAT of the incoming class which is close to yours... so for example on the US News site, we'd be talking about schools ranked 20-50 for example.... (approximation here). and you can start by looking into those programs and seeing which ones are the ones that fit you best.
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