Dear Hellman, Enlightenment comes from Grace.
There is no sure-fire way to prepare for it. One person
could say mantras for decades and live in the presence
of an enlightened saint, and yet never attain the
realization of enlightenment because they were so full of
spiritual pride, while another could have led their life as
a "sinner" and suddenly see the folly of their ways
and attain the divine state that is our birthright.
Mantra is a wonderful practice and has great potential,
but intention is very important. If you just want to
be able to say "I say my mantra for more hours a day
than you do", the mantra will probably not be too
helpful towards your spiritual growth. Similarly, every
"real" teacher seems to have incredibly unevolved people
around them. The thinking is that they are the ones who
need the teacher the most. There have been many
saints, like Swami Sivananda, and Sri Nisargadatta who
only had very brief contact with their Guru's, and yet
attained the highest states of Enlightenment. Their
intention was selfless, pure, focused, and determined. To
be sure, many, many people have chanted mantras and
attained Enlightenment. Similarly, Swami Vivakananda had
Enlightenment transmitted by his teacher's touch (Ramakrishna).
But it still comes down to Grace. When the universe
needs us to receive a mantra, or have a teacher, or
attain Realization of Enlightenment, it will happen. And
we will live happily ever after.