Watch the taxi drivers, some are good and others will cheat you. I have the benefit of being with someone who speaks the language and knows the culture. I could see getting taken advantage of if you don't speak French or Arabic. the funny thing is, they will pick up 4-5 differnt people even if you are not together.
Unique Suggestions: The great thing is, you can get to most of downtown by walking. Or, you can see if you can hire a driver.
WHAT ELSE CAN I SAY!? this is a developing nation... hence a price is never fixed, especially if you're buying souvenirs, traditional crafted items... of course that is if you're buying a few pieces.