It is definitely a very long and extensive process, but I think the key to gaining admission is to thoroughly research the process and have a system when applying. Have a binder with tabs for each school, how many seats, what the requirements are and any notes specific to the school ( name of program, director, what is unique about the school, any stats regarding admission you have come across). This will not only aid you in applications, but will also help you in interview prep.
For me, all of this research took the most amount of time, not studying for exams etc. exam scores, TOEFL etc are basic requirements but admission is gained on the rest of your résumé, including how well you have written your SOP.
I think the system is not well understood by FTD's, as in many parts of the world, exam score rank is the only basis for admission, which only small component for DDS/DMD here. You really need to be well versed in the admissions process in North America to be successful. Be very aware of what is valued for admission out here (volunteer, research, shadowing, MPH, PhD's, assisting etc), and that is what you should work on.
And lastly, the interview is a supremely important part of admission. You should prepare for those just as hard as if it is an exam.
I hope that helps!