If you want real results from this practice its important you put your self in to it 100%.
40% effort will result in 40% results.
Consistency is key.
If you can only chant 10 minutes each morning and night, try to stick to that. (Obviously family life and work can sometimes get in the way, but try to chant at least that much each day, even if you can not sit down in front of the Gohonzon or your place of practice.)
Effective Nichiren Buddhist practice is; Faith, Study and practice. Daily.
But how can we have faith in something we have never done before?
Buddhism does not ask you to believe in anything out side of your self, it asks you to believe in you, in your own infinite potential.
With regular practice you will begin to see how much value you bring to this world, who ever and where ever you are.
People say chanting even just one daimoku is effective, but I do not agree. That said; I think some daimoku is better then no daimoku.
But in my opinion it takes a while to develop strong faith and this can only happen with regular study of the Gosho (http://www.nichirenlibrary.org) and other Buddhist concepts, as well as strong daimoku daily. (http://www.sgi.org/buddhism/buddhist-concepts/)
Just chanting alone is not enough, it is important you grasp the concepts of Buddhism so you can effectively make changes in your life and see the benefit.
Nichiren Buddhism is a three pronged attack: FAITH, STUDY & PRACTICE. If one is missing there is no Buddhism.
As the saying goes, you can not become rich by watching your neighbour counting their gold.
You must fully engage with the practice and seek #actualproof
So if you have just started and you have your doubts, TEST IT.
Put your self in 100% for 1 month, really challenge your self.
You really have nothing to loose.