Anshei Knesset HaGedolah, in their wisdom and Divine inspiration (ruach hakodesh), included all the ideal aspirations of Am Yisrael in the wording of the prayer. They meticulously chose every word until a perfect wording was established, with which the Jewish soul can express itself before its Creator in the most supreme manner possible.
Even so, if a person wishes to add requests of his own in the middle berachot, he is permitted to do so. However, in the first three berachot, which are intended to praise Hashem, and in the last three, which are intended for thanksgiving, it is prohibited to add personal requests, so as not to detract from their general purpose (Shulchan Aruch 112:1; 119:1).
The personal requests permitted in the middle berachot must be related to the theme of the berachah. For example, if a person in one’s household is ill, one should pray for him or her in Birkat Refa’einu. If a person is in need of a livelihood, he should request that in Birkat HaShanim. If he wants his relatives to make aliyah, he should pray for that in Birkat Mekabetz Nidchei Amo Yisrael. However, out of all the berachot, Birkat Shome’a Tefillah is special. In it, one may make all types of requests. Since it concludes the blessings of request, it includes all of them. When one adds his own personal petitions, he begins reciting the established wording, and just before the concluding sentence, inserts his request.
Not only is it permissible to make personal requests, but according to many, it is desirable to do so, since the personal prayers that one adds emerge from the depths of his heart and arouse kavanah. Nevertheless, it is advisable not to prolong one’s personal appeals in the Amidah, not even in the berachah of Shome’a Tefillah, because the essence of prayer is directed towards the needs of the community as a whole, and when numerous personal requests are added, the communal character of the prayer is altered. It is best that one who desires to add more personal prayers does so after he finishes reciting all the berachot and says “Yih’yu l’ratzon…” since everything recited after that is not considered to be the main part of the Amidah. Rather, it is a relevant supplement to the prayer, for as long as he has not yet taken three steps backwards, he still stands before the Holy One Blessed Be He (Shulchan Aruch, Orach Chaim 119:2; Mishnah Berurah 119:12).
A person must express his requests in the Amidah properly. Therefore, when praying for an ill person, it is correct to mention his or her name. L’chatchilah, it is good to mention the name along with the mother’s or father’s name. However, if the sick person is next to him, it is unnecessary to mention his name, for his intention is clear. (Mishnah Berurah 119:2).