Our Sages taught in Pirkei Avot (Chapter 4): “Rabbi Shimon says: Be cautious regarding the reading of Shema and prayer and when you pray, do not do so in a burdensome manner; rather, it should be like requests and supplications before Hashem.”
The saintly Shelah (Rabbeinu Yeshaya Ha’Levi Horowitz zt”l) quotes the Sefer Derech Ha’Chaim who writes that there are ten primary aspects which impact a person’s prayer positively or negatively. They are: Torah, novelty, necessity, language, movement, voice, preparation, entrance, neighbor, and time. We shall now briefly explain each of these points.
“Torah” refers to the idea that the more one delves in Torah by participating in Torah classes and the like, this aids one’s concentration during prayer because Torah causes one to come closer to Hashem and to cleave to Him. Thus, when one stands in prayer, one will not find it difficult to concentrate and pray in a supplicating manner.
“Novelty” refers to one composing new personal prayers within the blessings of the Amida. For instance, one should pray for one’s livelihood during the “Shema Kolenu” blessing and for a speedy recovery for those who require it in the “Refaenu” blessing.
“Necessity” refers to the idea that when one feels reliant upon the mercy of Hashem, one will then pray with much more concentration and fervor. For instance, if one’s child is ill, G-d-forbid, one will certainly pray from the depths of one’s heart. One must constantly feel completely dependent on Hashem’s mercy and this, in turn, will cause one to pray with utmost concentration.
“Language” refers to the idea that one should pray in the language one is accustomed to speaking. This is because the text of the Amida prayer was established in the language our Sages spoke in earlier generations. Nevertheless, one may add personal requests and prayers in the language one feels most comfortable with.
“Movement” disturbs concentration during prayer for some people and aids the concentration of others. It all depends on one’s nature.
“Voice” refers to some who are able to concentrate better when they pray somewhat louder (obviously, within the confines of what is permitted by Halacha) and others who have optimal concentration when praying less audibly.
“Preparation” refers to the idea that one should sit idly before beginning to pray, focusing only on Hashem’s utmost kindness to him and removing any other foreign thoughts from one’s mind.
“Neighbor” refers to the idea that when one prays in a serious environment among others who are praying properly and with concentration, this aids one’s concentration during prayer as well. One should therefore see to it to choose a place for prayer that is a serious and devoted environment. One should not pray in a synagogue where people speak during the prayer and treat it disrespectfully. (Similarly, when one takes one’s children to the synagogue, they should observe people acting appropriately in the synagogue.)
“Time” refers to the idea that should pray calmly and not speedily. This certainly aids one’s concentration as well.
In the Sefer Ohr Le’Zion, Volume 2 (page 69), there is a piece of advice quoted from Hagaon Rabbeinu Ben-Zion Abba Shaul zt”l to help boost one’s concentration during prayer which is that every time one concludes a blessing in the Amida, one should not immediately begin the blessing before contemplating the subject of the next blessing. In this way, one will maximize one’s concentration like the pious individuals in generations gone by who would wait a little before praying and their prayers were answered.