What is the most practical way to get to Shanhaiguan from Beijing? Is day trip possible?

It's possible that you do one-day trip from Beijing. You need to take D trains from Beijing Railway Station to Shanhanguan directly. The earliest one departs at 07:00 and arrives in 2 hours and 34 minutes. The first class seat costs 110.5 RMB and the second class seat, 92.5 RMB. When you get off the train, walk around 5 to minutes to reach First Pass under Heaven. If you want to visit Old Dragon's Head, then you may take No. 25 bus from the railway station.