How do I make up missed prayers, and should they be made up in full or shortened if they were missed while traveling?

Scholars have differed concerning the ruling on one who abandons prayer. A group held that abandoning prayer entirely constitutes major disbelief (kufr akbar) that expels one from the fold of Islam, and that there is no make-up (qada') due for them. The majority, however, held that the disbelief of one who abandons prayer out of laziness does not expel them from the fold of Islam, and that they must make up the prayers they missed. Making up missed prayers is more likely to absolve one's responsibility and to avoid the difference of opinion.