Formal:
* أَتَكَلَّمُ الْعَرَبِيَّةَ (Atakallamul Arabiyya) - This is the most formal and grammatically correct way to say it. It literally translates to "I speak Arabic."
Informal:
* أَنَا أَتَكَلَّمُ الْعَرَبِيَّةَ (Ana atakallamul Arabiyya) - This is a slightly more informal version, adding "I" (Ana) at the beginning.
* أَتَكَلَّمُ عَرَبِيًّا (Atakallam Arabiyan) - This is even more informal and directly translates to "I speak Arabicly." It's more common in everyday conversation.
More specific:
* أَنَا أَتَكَلَّمُ الْعَرَبِيَّةَ الْفُصْحَى (Ana atakallamul Arabiyya al-fusha) - "I speak Classical Arabic"
* أَنَا أَتَكَلَّمُ الْعَرَبِيَّةَ الْعَامِيَّةَ (Ana atakallamul Arabiyya al-aamiyya) - "I speak Colloquial Arabic"
Ultimately, the best way to say it depends on the situation and who you're talking to.