Quiet/ Loud Recitation of Women in Prayer
Women can recite the Fātiḥah and the other chapter of the morning, maghrib and ‘ishā’ prayers loudly or quietly. But if a non-maḥram hears their voice, it is preferable for them to recite quietly.
 
Mistakes in Prayer
The prayer of a person who makes a mistake in the recitation of a word, or a vowel is not valid if he makes this mistake intentionally or he is a blameworthy ignorant person (who can learn it); otherwise, it is correct. Of course, if one had read his previous prayers like that believing that they were correct, doing their qaḍā’ is not obligatory.
 
Definition of Dhikr
All expressions containing the remembrance of Allah are counted as dhikr; and the ṣalawāt upon Muhammad (s.) and His progeny (a.) is one of the best dhikrs.

Bismillāh and Intending a Certain Chapter
In prayer, it is not necessary to say "bismillāh al-raḥmān al-raḥīm" intending to be a part of a certain chapter.  

Prostration/Tayammum on Cement/Concrete 
There is no problem in doing prostration and tayammum on cement and concrete tiles, although it is a caution to refrain from doing tayammum on them.

Prostration on Tissue Paper
There is no objection to doing prostration on tissue paper made from wood and plant other than cotton and linen.

Prostrating on a Carpet among Sunnis
In masjids located in Mecca and Medina, one should prostrate on a thing on which it is correct to prostrate unless it contradicts the duty of dissimulation. 
 
A Turbah's Stain as a Barrier
If the stain on a turbah is so much that it forms a barrier between the forehead and the turbah, the prostration is void and so is the prayer. 

To Make an Extra Prostration
A person realizes that their forehead is not in complete contact with turbah. So they raise their head and place it again. If someone does so absent-mindedly or out of ignorance and they do so only in one of the two prostrations of each rak‘ah, then their prayer is correct and there is no need to repeat it. But if the action is done knowingly and on purpose or it is done in both prostrations of a single rak‘ah, then their prayer is void.

Forehead's Striking the Turbah Repeatedly
When doing sajdah, if one's forehead strikes the turbah twice unwantedly, it is considered as one sajdah.
 
Listening to a Verse of Prostration from a Radio
Upon listening to a verse that requires prostration from a cassette player, a radio, or TV, making prostration is obligatory.