I don't think I will surprise you by saying that without a doubt the most important monument in the whole town is the Church of the Nativity. The front of the nave houses a small cave where Jesus was supposedly born. The exact location is very precisely marked out on the floor with a fourteen-pointed silver star. To avoid the tourist crowds, I strongly advise that you visit very early in the morning.
However, Bethlehem is far from being a museum-town. It is very like many of the other towns in the Middle East, popular and densely populated, and always made lively by the merchants. I made a loop from Star Street, which runs from Manger Square, before turning into Pope Paul VI Street and ending up in the souk, attracted by the clamour and cheap jeans. It is a lovely walk and made even better if you are not afraid to lose yourself in the latticework of small streets in the old town.
Having arrived at midday, I made the mistake of beginning by visiting the most popular tourist sites straight away. I had to avoid the guides and taxis who wanted to take me to see the Banksy graffiti which had become a bit of a tourist trap, or the other cities in Palestine.
The emotion of the pilgrims is palpable in the Church of the Nativity but I was more or less disappointed, so I advise you only go in the morning or the evening to avoid the crowds.
Later, I visited the Milk Grotto which was much calmer and also more beautiful. I could eventually appreciate Bethlehem in the evening as I walked through the streets outside of the traditionally tourist area and could shop in the market like the locals. For dinner, I found a little falafel restaurant where I talked with the owner about the quality of life on the West Bank. For me, the best part about the city is the inhabitants who are both accessible and generous.
Bethlehem is a town that it's difficult to be indifferent to. If you are spending most of your trip on the Israeli side, going through the check-point at the "wall of separation" in order to get into Palestinian territory abruptly reminds you of the region's realities. And to get to the centre of town, the road goes along this famous wall. So it's difficult not to think about the political context.
But, of course, to go to Bethlehem is to go to one of the most important Christian sites in the world. Whether you are a believer or not, a Christian or not, being part of the fervour and exploring somewhere that is so important, both historically and spiritually, is absolutely unique. This visit is definitely unmissable if you are visiting the Palestinian territory.
Finally, I have to say that despite the weight of the history and politics, Bethlehem is a lively town, with a souk that's full of fresh local products (Olive, pita bread, za'atar, citrus fruit, manouche, baklava, etc.)