Take for example this practice I've been experimenting with of Papaji's, which is merely to repeat the admonition “I am free”. Here's Papaji's explanation of it (full text at this website, under the title “Who are you?”):
“When you still all activities, without doing anything, without thinking any thought - when you do not stir any thought from the mind ground, without moving, without moving the mind, without starting a single thought - in an instant of time you are free. When you give rise to any sadhana or practice, when you go to any center or ashram, when you go to any teacher or pilgrimage or church, when you make any prayer, you have postponed it. This you have done.
Be free of all these things right now. Because free you have been, free you are. You cannot achieve anything other than what you are. Anything gained afresh or achieved for the first time - anything which is new to you - you will certainly lose because it was not there at all. All that is natural to you is already there. Do not try to achieve anything or gain anything or attain anything which is not already there. This is not a fresh gain. People think, "At the end of this sadhana I am going to be free." But it is not like that. You have been looking for something else, not freedom. Freedom is already here.
When you exert effort or practice sadhana you will camouflage and cover the truth. You will have to remove this covering because it is you who put it there. This covering will be removed through your effort. And when all efforts are done away with - when all attempts, all intents and intentions, all ideas and notions are rejected - at that time ask yourself, "Who am I?" You will certainly find the answer.
This is how freedom is already attained: You are already free. If you can hear this once from a teacher you are free. If you cannot hear this, then practice. If you can listen to a teacher who is not a liar, who is speaking the truth, and if you are honestly longing for freedom then listen once and you are free.
If you are not honest and if the teacher is not authentic it will not work. You will have to take up a practice if something is false somewhere. What is that practice? At all times, walking, sleeping, dreaming, on waking, while standing, sitting, lying, go on chanting the mantra. I can recommend mantras also, as a second best. If you can repeat this mantra from now till your last breath I guarantee you will not appear again in a next birth; you will not fall into any womb. What is the mantra? "I AM FREE!" Take up this practice if you do not believe me.
If you can listen, if you long for freedom, and you feel that I am honest when I tell you that you are free, then accept it! Hear this only once and you are free.
If you do not accept what I am saying then I will give you a practice as a second best. You will have to continue practicing on every breath - every breath of the waking state, of the dream state, of the sleeping state up to the last breath. Then I guarantee that you will not appear again in this miserable samsara.
Here's what I find: this works. I'm noticing that most of my problematic feelings about life are simply based on the conviction of bondage, limitation, and restriction. Something impinges on my mind, and I believe it, I let it define me, and I struggle with it (or just give into it and try to accept it). Instead, this “mantra” of “I am free” cuts through that to the core, and lets me remember that this bondage isn't true, that I am truly free, for real. Repeating the admonition intensifies that feeling, that intuition, such that I can relax and surrender rather than feel cornered and resorting to the fight-or-flight mechanisms of stressful seeking. It brings an original, natural strength and balance to my disposition, to me feeling, and to my action. My mind relaxes, and my breath fills with life-force.
Now, I'm not practicing this with every breath – far from it. But even practiced every now and then, it seems to work as advertised. In other words, it's helping cast out some of my doubts, and replacing them with a basic sense of faith. Slowly, to be sure, but slow is better than nothing.
One other thing I'll say about this practice is that, for me at least, it isn't a mantra. I haven't really tried to use it as a mantra, at least not in the traditional sense. For me it's the meaning of the words that matter, not their repetition. A mantra as I understand it is some word or phrase that is repeated to the point where it no longer means anything, it's the sound itself that matters, or the connection it creates with one's God or Guru. Mantras are supposed to carry some magical resonance to them, such that merely repeating them creates a force of sound and psychic force that in itself produces some kind of effect. I don't find this to be the case with “I am free”. I mean, its power come directly from its literal meaning, not from some magical power within it. It directly connects me to the simple reality that I am free. In fact, the reason I think I find myself more drawn to this form of mantra, more, say, than “I am Brahman” as Papaji and others also suggest, is that I know immediately what the word “freedom” means, whereas I have to do a kind of translation process in my mind with the word “Brahman”. In essence, they mean the same thing, but the meaning is more direct and clear to me using the word “freedom”. What the hell is “Brahman” anyway? I'm not a Hindu, after all. The word is a bit loaded at this point, like using the word “God”. If I were to repeat “I am God”, I think I would encounter a fair amount of confusion and resistance, because of all the oddball connotations associated with the word. Whereas “Free” is, well, free of those things.