First of all, let me say that there are not many programs that you can apply to without any experience. HBS 2+2 and Yale Silver Scholars are the exceptions. In Europe you also have a Management degree for new graduates called a Masters in Management, which you can look into if you are interested.
Now, HBS 2+2 is a very very very tough program to get into, so even if you get a 780 on your GMAT the chances of your acceptance will be slim. You can apply, and should if you have a strong GMAT score and other things, but not with the expectation that you will be accepted. An MiM degree is an option, but it is a replacement for an MBA, and it means that you will not do an MBA later. LBS's MiM is the best one out there, and whether you prefer that or an MBA is up to you.
Otherwise, to prepare yourself for the MBA, the BEST thing you can do is to get the best job possible. If your intention is to apply to top schools, then you want to try and get into a feeder firm for those schools (McKinsey, certain govt' jobs, PE, big IB banks, etc.), and then of course do very very well in your workplace!
I hope this gets you started, and if you have any follow up questions, don't hesitate to ask.
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