The Saum (fast) of Ramadhan is Fardh (compulsory) upon every sane and mature Muslim. One who denies the fasts of Ramadhan as being Fardh becomes a Kaafir (i.e. he loses his Imaan), and the one who accepts it as Fardh, but neglects its observance, is described as a Faasiq (a flagrant sinner).
Eating, drinking, or having intercourse will invalidate the fast.
The penalty imposed by the shariah on a person who deliberately, without any valid shar'i reason, breaks his fast is known as Kaffarah (i.e. the person will have to fast for sixty (60) consecutive days, one after the other, without missing any day in-between [Shaami, vol.3 pg.386]
Special care should be taken when rinsing the mouth so that water does not go down the throat. While fasting, one should not gargle, instead he should suffice on just rinsing the mouth.
Ladies should take care that no water goes into the private parts at the time of istinja (washing the private parts).
Applying eye drops into the eyes does not invalidate the fast.
Applying surmah (antimony) into the eyes will not break the fast, even if the color appears in one's saliva or mucous in the nose [Shaami, vol.3 pg.366].
If while making wudhu water slips down the throat, while one does not remember that one is fasting, the fast will not break. However, if water involuntarily goes down the throat while the person is aware that he is fasting, then the fast will break and Qadhaa will become Waajib (compulsory).
Administering ear drops or oil into the ears will invalidate the fast [Shaami, vol.3, pg.376]
Putting any medicine into the nose will invalidate the fast [Shaami, vol.3, pg.376].
It is permissible to receive an injection or vaccination while fasting [Mahmoodiyah, vol.11, pg.87]
Deliberately inhaling the smoke of Loban, Agar Batti, or cigarettes will invalidate the fast [Shaami Vol.3 pg.366].
Swallowing one's saliva will not invalidate the fast, irrespective of the quantity.
If a person vomits involuntarily, irrespective of the quantity, the fast will not break. However, if the vomiting is self-induced, it will invalidate the fast if it is a mouthful. But if it is less than a mouthful it will not invalidate the fast (even though it was self-induced).
It is not permissible to use inhalers (used for Asthma), while you are fasting. The use of it in the state of fasting will invalidate the fast.
It is permissible to apply lipstick while fasting; however if there is a chance that it will enter the mouth then it is Makrooh. [Ahsanul Fatawa Vol.4 pg.434]
If a woman undertakes a medical test, in which an instrument is internally inserted, then her fast will break, and Qadhaa becomes Waajib [Shaami, vol.3 pg.369].
A woman is not permitted to insert a tampon whilst she is fasting.
A pregnant woman or breast-feeding woman is permitted not to fast if she fears for her life or the life of her child. She must fulfill the Qadhaa of the missed fasts at some later stage. However, if no fear exists for the safety of the woman or her child, then it will be sinful to forego the fast. [Shaami Vol.3 pg.403]
If a person caresses his wife or derives pleasure from any part of her body except having intercourse in one of the two private parts of the female i.e. front or back (back-although not permissible under any circumstances) and ejaculates in the process, his Fast will break, thus making Qadhaa necessary upon him. Kaffarah will not be necessary. Thus, he will have to compensate by keeping one fast only. However, if he does not ejaculate in the process, then neither Qadhaa nor Kaffarah will be necessary upon him. [Shaami, Vol.3, pg.371].
What has become a common practice in this era is that many people relax and indulge in futile discussions while the Imam is reciting the Holy Quran during Taraweeh Salaah. When the Imam is about to perform Ruku, these people will quickly join the Salaah. This act is Makrooh and it shows the inert nature of a person and is a sign of a Munaafiq. It is stated in the Quraan "And when they stand up for Salaah (the prayer) they stand with laziness" [Nisaa 4:142].
The television being an instrument having been devised and made up primarily for the dissemination and circulation of sin and vice is totally prohibited in every avenue of its usage. Television brings its viewers a steady stream of programs that are designed to entertain the people and drive them away from Islam. The "entertainment", comfort, and raahah of a believer is in fulfilling the commands of Allah Ta'ala. Therefore, during this blessed month, we should abstain from everything that is abhorred by Allah Ta'ala.