> Constantly: mentally or as a very low whisper throughout your day as you can during alone moments for e.g. driving, walking, showering, toilet, etc. In my > 4 year experience of practicing constant prayer, I find that praying short psalms mentally (one can work on memorizing 2 at a time) and praying the Jesus Prayer (“Lord Jesus Christ, Son of God have mercy upon me a sinner”) as a low whisper works out best. Or if you are praying in your room at home by all means you can pray the Jesus prayer audibly at a normal volume. Alternate between the Jesus prayer and short psalms. Experiment and try to discern what is working for you. Praying the Jesus Prayer alone should be easier as it is shorter and easier to memorize but for the beginner it can be extremely boring and tedious to pray a single thing. Hence mixing it up with psalms is good too. In anything in life, variety helps us a lot lest we go insane!
> Slowly: Pray the words slowly and with pauses. Take micro breaks as you need after each word as well as after each time you complete one jesus prayer. Breaks helps us to be more attentive and refresh. Praying a little bit for however many seconds we can, then taking a break, then praying a little bit again according to our spiritual ability, then break and repeating this …. is BETTER than praying a long time with no breaks as this is too too hard for beginners – the mind is too unstable. We must always pray according to our current spiritual energy, level and ability. Over time, it becomes easier, God’s grace comes.
> With humility: This is the most important thing in the beginning. Pray above all with great humility and holy reverence – realising our great sinfulness and unholiness and that we have very impure thoughts and desires. Feel a need for Christ, for His grace to calm you in your sufferings/tribulations and your need for Him to clean you from all your sins i.e. your lustful, greedy, envious, bitter, angry and hateful thoughts and feelings and especially your primary and biggest sin. The person who doesn’t pray with humility and with the only intention of seeking purification, holiness and repentance are causing themselves harm and the devil can delude them. This is why it is useful to read perhaps 4-5 good articles of the lives of the saints (or alternatively a book or two) before you begin to practice constant prayer. The lives of the saints humble us and inspire us, making us realize our sinfulness and that we are not so holy and saintly as we think we are.
> With attention: Struggle with all earnestness to be attentive to the words of the prayer and to let the words echo into your heart. As St Theophan the Recluse says, “understand what you read and feel what you understand … No other rules are necessary … These two – understanding and feeling – have the effect of making every prayer fitting and fruitful.” You should know that this striving to be attentive to the words of the prayer is what is the most difficult thing about prayer. Whenever you read about “struggle” in all and any Orthodox writings it mainly refers to this phenomena – the struggle to be attentive to the words of the prayer. Whenever you feel your attention was chased away and you have insufficiently felt the word in your heart, simply repeat the same word of the prayer.
> Extremely patiently: Don’t overforce the above struggle (although it still requires force), greatly knowing and accepting the fact that the fruits of this labour comes not quickly but with much patience, much time and much much persistence. God’s grace comes ONLY to the patient struggler and never quickly except for the extremely rare cases. Hence with this knowledge of the importance of patience, we understand we should not despair either or become disheartened or seek fruits too early.
> With faith: we must believe that Christ exists, He hears us and that He alone is the Saviour of the soul. He alone can defeat the demons within us and relieve us from the disease of sinful thoughts and feelings. Only His grace can destroy the work of Satan within our hearts. It cannot be done by will power!
An example in writing to demonstrate the above instructions is: Loooord Jesussss Jesussss Christ Christ Christ Son of God, have have mercy mercy upon upon me a sinner sinnerrr sinnner. Take breaks as needed.
All of this is just a guide. Reading is always just a guide and a source of tremendous inspiration and humility. The best knowledge comes from your own experience which is acquired over time in trying to struggle to apply what you read. Everything comes with 1) Patience, 2) Constant struggle 3) Never despairing/giving up. There are people who make progress in these things without much reading, but nevertheless reading is extremely useful and is a fence for us against practicing spirituality incorrectly.