To write Arabic letters, obtain a reference depicting all 28 letters in each of their forms. The best resources also contain directional arrows outlining the movement of the pen for every letter. Continue practicing until the result is clean and smooth and writing right to left comes naturally.
Arabic is always written in script or cursive, which means that there is no such thing as printed letters. Consequently, as with all cursive systems, special emphasis is placed on mastering the fluidity between interconnected characters for legibility. Each Arabic letter can have up to four forms, depending on where it appears in a given word, and all these forms must be memorized. However, this should not be overly intimidating, as learning English cursive presents the same basic challenges, and variations in Arabic letter forms are often slight and easy to remember.
The Arabic alphabet is an abjad, meaning it containing mostly consonants. As a result, vowel sounds often appear in small dashes or loops located above or below the letter. These, too, must be memorized, though there are only a few to learn. As with learning English letters, it is helpful to have ruled paper for practice to stabilize the hand and to begin recognizing which letters rest on the line and which have elements falling below it.