I might repeat points of previous commenters - but then repetition is key to understanding, right?

Okay, your question sort of implies what would you do differently, and what did you do right.
1) Get the GMAT out of the way early. There is nothing like the real test, never mind those test exams. You might have to take it again, leave SUFFICIENT time in between those tests to think about a new study strategy (I changed mine completely after a mediocre first try)
1a) This applies to the TOEFL as well. I got my TOEFL too late because they didn't have available testing slots until late October. That screwed up my R1 Kellogg app.
2) Think about schools. river outlined that well.
3) I bought Montauk's book when my application process started. That one gave me quite a few hints as to
what to do
when. (buy that thing EARLY!

)
4) Try to get applications done in the first Round. Start with the one that matters least. (some people will recommend starting with Kellogg if you apply there)
5) Leave enough time for writing essays. Find people that will help you and give you feedback.