From Taipei Main Station and catch a train to Ruifang, if you have an easycard you can pay with that. At Ruifang, get off and go to the ticket office. Ask for a day ticket on the pingxi line. This means you can get on and off where, and as often as you want on the Pingxi line.
From Taipei, the trip takes an hour to an hour and a half, and the train from Taipei will be packed at the weekend, so leave early.
The Pingxi Line (平溪線)
The Pingxi line is a small railway which takes you to the heart of the mountains. Perhaps most famous for its sky-lantern festival, 2 weeks after Chinese New Year, this area is worth a visit all year round. A great day trip from Taipei, the train takes you past high peaks and through picturesque villages where you can stop and have a snack in the little shops, or take walks in the surrounding mountains.
Shifen is one of the the first of these villagesm and a mere 25 minute walk from the train station is a large waterfall. To get there just follow the signs from the train station. It's quite impressive, but unfortuntaley they make you pay to see it.
Pingxi & Sky lanterns(平溪/天燈)
Pingxi is where the sky-lantern festival takes place, but you can light your own whenever you want. Just go into one of the shops on the train tracks and they will ask what colour you want (don’t worry, you can just point) and they give you some paint and a brush. When you’re ready you’ll be taken outside and they will light it and tell you when to let go. It’s wonderful to watch it disappear into the evening sky.
The final stop on the line is Jingtong, a lovely village built around a flowing river. Here you can wander around the sloping streets or sit and relax, enjoying a cup of local tea. We went to a teashop in a whimsically decorated room facing the river. You’ll find it easily because there’s a piano on the first floor. As Jingtong is the final stop on the line, finding a seat on the train will be much easier!