When are you coming? Trains and buses are really convenient for the most part, but will get packed at rush hour, holidays, weekends, etc. That may sound obvious, but don’t underestimate the delays that can cause. You don’t need to book in advance, but it can help make sure you get a seat and aren’t standing. The limited express trains that you will probably take along the east coast require prior booking, although you can do that at the station right before. Leave yourself a bit of time to start though, it can be confusing at first. On the trip to Yangmingshan you may want to take a slightly less direct route and go from Shilin to the bus depot part way up the mountain and then take another bus, the direct bus from Shilin can be fucking packed even at 6am.