Below are a few books I recommend reading prior to a trip to Syria:
Syria - A Historical and Cultural Guide, by Warwick Ball
Damas - Miroir Brisé d'Un Orient Arabe (Éditions Autrement, Séries Monde)
Monuments of Syria - An Historical Guide, by Ross Burns
Syria - A Selection of Reports, by Carol Miller
Damascus - Hidden Treasures of the Old City, by Brigid Keenan (illustrated)
Damascus - A History, by Ross Burns (a detailed historical account, recommended only for those passionate about the details)
Rome in the East, The Transformation of an Empire, by Warwick Ball
Les Croisades vues par les Arabes, Amin Maalouf (The Crusades Through Arab Eyes, by Amin Maalouf)
Miscellaneous: It is impossible to get any Syrian Pounds overseas (except in some Arabic countries). There is a FOREX outlet just outside the arrival hall which accepts USD and EURO. Remember to change all the Syrian Pounds to foreign currency before you leave!
Winter can see temperature dropping below zero. Bring some warm clothing if you are traveling in winter.
Miscellaneous: Better have a torch light or some candles (with lighters) handy. The electricity supply in Syria is notoriously unreliable. Daily power cuts upto few hours are very common during winter and summer.
It's a good idea to bring a flat drain stopper. the hotel wash basins have the drains with the pierced metal piece in them. However, there were no stoppers, so handwashing clothes in the basin is difficult because the water just runs out. Since I did not find coin laundries in Damascus and laundries where you hand in you clothes to get them back washed and ironed are pretty expensive, you might handwash a few things.
I also brought along a laundry line with little suction cups that Iattached to both walls and dried my clothes like that.
One more useful thing are plastic flip-flops. There were never any bathmats in the bathrooms and although I drew the shower curtain I somehow always managed to get everything wet in there.
Women should bring a headscarf to enter mosques.
If you go in winter, take some very warm clothes as it get's surprisingly cold. My friends in England all laughed when I said it was freezing, but although it probably isn't as cold as England is, in Syria you feel it more because most buildings (hotels and especially houses) are inadequately heated, so it is impossible to get warm!
Toiletries and Medical Supplies: You can get all kinds of toiletries and medical supplies (except good cough tablets) in Damascus.
Photo Equipment: Films bought in good shops usually work fine, but outside Damascus and Aleppo, films should be treated dubiously! I got most of my films developed in Syria, and had no complaints. Any Kodak shop is good, as is the Photo Misr not far from the Cham Palace Hotel in the New City. You can normally get same-day service.
Passport photos can be taken in most of these shops (sometimes called studios, although that's a wee bit optimistic), although don't expect wonders - mine were taken using an antique camera (the photographer had to cover his head with a dark cloth!), but at least they were cheap. You will need countless passport photos for obtaining and extending visas (they always ask for one more than you've got, so be prepared!)
Luggage and bags:
Bring comfortable flat shoes ,and I suggest to avoid white tennis shoes ,Specially in the winter time.
and on Summer advisable to put on men's sandals since the weather is too hot.
Miscellaneous: Don't forget the romantic aromatic candels, because they will make all the difference...