Mt. Fansipan is a very steep mountain that gets a lot of moisture. Those looking to climb it should be in good shape and prepared to to have muddy wet feet. The scenery is incredible remember to bring a camera. For most of Vietnam having a rain coat is a little excessive because it is so warm. On the mountain having a rain coat is not a bad idea especially at night. The trails around Sapa are a lot of fun.
The popular trails
Day 1: You start going through several different valleys with a lot of lush jungle. The first day entails 2-4 hours of hiking. There is typically a lot of mud so come prepared. You might have the option of moving up to a high camp but the camp right by the river is beautiful. Enjoy the river to clean off.
Day 2: From the camp, you pretty much go straight up the mountain side. It is a mixture of light third class rock, root and tree climbing. The trail can be very slick and there are a lot of spots where the trail drops off. If you have trouble with heights you might not want to consider this hike. From the camp it takes 2-5 hours to reach the summit. Going up is not to bad but if it rained recently the trial can be very slick. Coming down is where you want to be careful.
Day 3: From the camp it takes about 3 hours to get down, be careful about grabbing on to the grass if the trail is slick it will tear up you hands. When you reach the bottom you will end up in a beautiful hill tribe village.
If you have your own tent and sleeping bags, you can arrange to camp on the mountain. Tents and sleeping bags can be hired from Active Travel Vietnam. If you can I recommend you bring a sleeping bag that is rated to at least 40 degrees. It can get a bit cold at night.