Understand the culture
Respect local laws and customs. Dress in a modest way, covering at least the tops of arms and legs, and not tight clothes. Although, in practice, anything goes, it's best to respect the culture of the land that you are visiting. Don't behave in a manner that might insult Muslim customs or beliefs. Don't swear - as you can get fined and sent to jail! Public displays of affection are frowned upon.