Dear Paappi ji,
different people may give you different valid replies, but that much in simple words I may tell you that there are 3 stages.
The first one is of realization.
Here one realizes the importance of this type of bhakti of meditating of which you are asking.
We all agree, we are sinners, and our sins are the huge barrier between us and our beloved Lord Waheguru. Therefore we want to get purified with His grace, in order to go there where He is and merge in Him.
In this respect the Bani tells us:
ਪਤਿਤ ਪਾਵਨ ਹਰਿ ਨਾਮਾ ॥
Pathith Paavan Har Naamaa ||
The Lord's Name is the Purifier of sinners.
So firstly, we realize that if there is any such thing which can purify us, is that one of meditating on His holy Name only.
Then the second stage is the one of application.
Means, we have to apply to a practical method, a jugtee, or let us say Bhakti, in order to reach our goal, of that which one, that we realized its supreme importance in the first stage, and as said, it was of getting purified.
Now here once again, different questions may arise in different minds, some may ask, how much time should one engage in this practice.... minutes? hours? days? timings? Or some may even think of substituing it with other practices, for that is what they have mainly seen others doing...
But fortunately we have Guru Jee with us, to remind and correct us, and bring us back to the right path again and again, for as Guru Jee tells us :
gur satgur kaa jo sikh akhaa-ay so bhalkay uth har naam Dhi-aavai.
One who calls himself a Sikh of the True Guru, shall rise in the early morning hours and meditate on the Lord's Name.
Not only that much, rather Guru goes a step further by telling us :
Kirapaa Keejai Saa Math Dheejai Aath Pehar Thudhh Dhhiaaee ||
Show Your Mercy, and bless me with such understanding, that I may meditate on You, twenty-four hours a day.
Some may protest and say, why 24 hours?
This also has an explanation, Guru Jee never says anything without a solid reason. Though it is clear, that in the early morning hours we should meditate on Him, but, when He says all the 24 hours, it means, all the maximun time possible should be done, while eating, walking, waiting, jogging, bathing etc.... every step towards Him counts in our favor, for having kept His name the maximum time of the day in our minds, then the result is, that we are unconciouslly subduing the mind, so, when on the next day we sit to meditate in the early hours, our mind will be almost groggy and will not be able to play mischiefs with us, by distracting us with its countless thoughts being poured continously....
The the other reason for which Guru Jee tells us to meditate on Him, all the 24 hours, that is becuase He knows how stupid and weak we are, so in this way, we will focus only on what He wants us to do and not do any sort of manmat of our which we usually do....
And the last and third stage, is that of transformation.
In this respect the Bani says:
Jin Har japeeya se Har hoeeya.
He who repeats His Name, becomes Him.
Thus we are transformed by getting purified with His name, from an alone and a wandering soul in pain, caught in the net of the ceaseless chaurasee ka chakar, into the Infinte and blissful Waheguru Akal Purukh.
This in short, is the mahima of Waheguru and the bhakti of meditating upon His Nao, His Nam, Satnam...
Stay blessed.
SSA.