I know Om Mani Padme Hum is a very common mantra for many people, but not many people know how to use it.
This chanting brings great healing, cleansing, protection, and life changing. This chanting will bring you to a divine place when your life ends, and that place is full of divine beings. The more you chant, the more powerful it gets. You cannot expect a miracle after chanting a few times. The requirement of chanting Om Mani Padme Hum is 1,000 times a day at least, the more the better. After you chant it for a long time, your spiritual energy will increase, and you will feel it very soon.
Here is what you can do with the mantra.
Before you drink a cup of water, juice or tea, Chant about 7 times Om Mani Padme Hum and blow it into the beverage, and then you drink it. After you chant it, the beverage will turn into a blessing drink.
I prefer you do this everyday, there are many different types of spirits out there in the world. There is a type called "Hungry Ghost", they are hungry, but they are not allowed to eat because their throat is on fire. So you can help them by chanting Om Mani Padme Hum on some food like bread or cooked rice, and then leave it under the trees or bushes. (Don't use meat, vegetables or grains are fine). After chanting, the food is now allowed for those spirits to eat, and even animals eat it will get blessed.