Uncompromising
One who is yotzei his chiyuv with keviyus ittim must not interrupt that time, even if he thinks he can make a great profit (שו"ע או"ח סי' קנ"ה ס"א ), since the main value of keviyus ittim is when he doesn't skip a single day (סדר היום בסדר הלימוד ), unless he is a total oneis (נצח ישראל להח"ח פי"ב ).
The Time
How much? There is no specific amount of time one must set. It all depends on the amount of time he has (סדר היום ).
When? Ideally, one should set aside the same time every day (כף החיים או"ח סי' קנ"ה ). It is best to designate a slot right after davening, to fulfill the posuk, "yeilchu meichayil el chayil," and to avoid getting engrossed in his affairs and missing his learning (מ"ב שם סק"ג ).
Nighttime. One must also learn at night. One who desires to get the "crown of Torah" must take care to spend his nights in words of wisdom and Torah; not sleeping, eating, drinking, and chatting (שו"ע סי' רמ"ו סכ"ג ), since most of the wisdom a person learns is at night (רמ"א שם ).
Making up. If one learns a certain amount or at a certain time each day, but was busy one day and skipped, he must make it up at night (שו"ע או"ח סי' רל"ח ס"ב ). He should not push it off until the next day, since the next day has its own chiyuv (מ"ב שם סק"ד ). Bedieved, some say making up on another day works (פתח"ת יו"ד סי' רמ"ו סק"א ).
Place
A set place. One must set a fixed place in the beis medrash for learning Torah (רמ"א או"ח סי' קנ"ה ס"א ).
Learning at home. Even after learning in a beis medrash, one should set aside time to learn in his house. As the Mechaber says, "Fire consumes any house in which words of Torah are not heard at night" (שו"ע סכ"ד ). It is good for his wife and children to see him learning, since the Torah will influence them.
A room to learn. Even when learning in his house, one should designate an area where he will not be disturbed. If possible, he should have a room specifically for learning Torah, and treat that room with the kedushah of a beis medrash (קב הישר פנ"ג ).
