One of the most important yet simple decisions you can make to support your application goals is the order you submit your applications and the order of your interviews. Let's assume you are applying to five schools: 2 dream schools, 2 core schools, and 1 safety school. I would recommend the following for consideration...
1. Begin your dream school application first, but turn it in last.
Your first application will be the toughest because everything will be new. Subsequent applications will inevitably be a variance of your original. By the time you get to your fourth or fifth application, they may only require a slight alteration of your existing investment. Your dream school should be your main effort... assuming you have a decent chance (20%) of getting in. Work on your main effort first. This will set the tone and increase your chances elsewhere, since you will be much more excited about your dream school application anyway.
You also don't want your dream school application to just be a shadow of your safety school application; it should be the other way around. But there is a second part to this rule. Turn in your dream school application last. As you go through applications two, three, and four, you will learn more about yourself, and more about how to relate your story. You will also have more time to reflect on your essays and improve your style. So my suggestion is to complete your main effort school choice first, and then put it down. Submit it last. As you go through your other applications, occasionally pick up your first school choice application and re-read it. You will see that there are always improvements to make.
2. Submit your applications in reverse order of priority
If you submit for your safety school and a core school in round one, you will be much better prepared to submit for your dream schools in round two. First, you will have an additional 10 weeks to reflect on your essays, receive feedback from current students and alumni as you continue to network, and you should also hopefully have an interview experience at least from your safety school. All these experiences should improve your main effort, and if you really want to get into your dream school, this will help those odds. The flipside is that of course you incur more risk by applying to your safety school first, because by my own logic, it will be your weakest application. That said, I don't think many people get into any dream schools without incurring some risk in their approach.
3. Apply to your safety school in round one; dream school in round two
Having one acceptance under your belt will give you a lot more confidence and alleviate the inevitable anxiety that will accompany waiting for second round decisions. This is only true if of course you will be satisfied attending your safety school. Never apply to a school that you will not be satisfied attending. It's a waste of time for everybody. The extra 3 months between rounds will also give you more opportunity to improve your essays and prepare for your interviews.
4. Interview in reverse order of priority
There are many ways to practice for your interviews... practice with friends, practice in front of the mirror or on video, brainstorm anecdotes, mock interviews, etc. But the best way to improve your interviewing skills is to actually interview. You will get better and better with each interview, as there is nothing that replicates game day like getting out on the field itself. It might fall outside of your control, but if you can, schedule your interviews in reverse order of priority. Safety school first, core schools second, and dream school last. If you are fortunate enough to receive multiple interview invitations, you will be highly polished for your main show... your dream school finale. Given the mediocre performance of my first interview (a full 3 months before HBS), there would have been little chance of acceptance at HBS.
5. In conclusion
If you are willing to incur some risk to gain admission at your dream school, consider a strategy as described above. Never apply to a school you are not willing to attend. I've read from many people posting "I only got into my safety school. I'm going to reapply next year." Don't bother applying anywhere if you are not truly willing to attend. Some people only apply to Harvard, though I don't recommend applying to only one school because you learn so much by going through the application process.