As we round out our series on entrepreneurship through acquisition (ETA), let's talk about when the rubber meets the road: getting into the day-to-day running of your new business.

We've already discussed what ETA is and how to get started on the path to owning your own business, as well as where to begin looking and what to look for when buying a company. Now, you're ready to get your hands dirty and test your entrepreneurial grit at the helm of your new business.

The biggest hurdle in this process is ensuring a smooth ownership transition. When done strategically, this can alleviate numerous headaches and problems while keeping the business moving forward despite changes at the top.

Finally, once the transition is complete, I will offer guidance on what success in running your business could look like.

Related: Want to Start a Business? Consider Buying One Instead — Here's Why.

Before you get the keys to your new kingdom, you'll want to do a few things to prepare as your first day as owner approaches.

In my experience, the first 90 days are the most challenging yet most critical part of the transition.

Before you step into the office on day one, you must have a firm plan for this time and closely adhere to it. Otherwise, things can go sideways quickly.

Your first order of business is to........

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