Need cash when I land, best place in Lebanon? Airport or places in the city?
My advice is to skip the airport exchange entirely. The rates are terrible, and you'll lose a lot of money. You'll get a much better rate at a money changer in the city. The Lebanese pound has a highly fluctuating value, and the unofficial rate is much better for you. I've had good experiences at places like Trad & Srour Exchange. Just make sure to check the daily rate online before you go.
The airport exchange counters have awful rates. Your best bet is to find a reputable currency exchange center in the city. I've used places in Hamra and Beirut Souks. The unofficial market rate is much better than the official bank rate. You must have US dollars with you, and it's best to have clean, new bills. Don't exchange large amounts at once, and always count your money in front of them.
Don't even think about using the airport exchange. It's a complete scam. You will get a much better rate at a licensed money changer in the city. The country's economy is in a difficult state, and you'll get a much better rate for your US dollars from a private exchanger than you will from a bank. My advice is to find a trusted one in a neighborhood like Hamra and exchange there. It's the only way to get a good rate.
You should absolutely avoid the airport exchange counters. They give terrible rates. Your best bet is to go to a reputable money changer in Beirut. Due to the country's economic crisis, the official bank rate and the unofficial black market rate are very different. The black market rate is much more favorable. I've had good luck with places like Assi Exchange Company or Zouein Exchange. Just be discreet and count your money carefully.