Many sites assume they're "Arabic" the moment dir="rtl" appears on the <html> element. The reality is much deeper.
1. Directional icons
A "forward arrow" must flip. A "save" or "search" icon must not.
2. Numerals
Hindi numerals ١٢٣ or Arabic 123? The choice varies by audience and market.
3. Dates
Gregorian or Hijri? Both? The right answer is usually to let the user choose.
4. Number formatting
Comma-separated (1,000) or dot-separated (1.000)? In Arabic the dot is standard.
5. Fonts
A beautiful Latin font doesn't mean it suits Arabic. Look for typefaces designed specifically for Arabic.
6. Line wrapping
Arabic words run longer. Test your layout against genuinely long headlines.