By train. Golmud sits on the Qinghai–Tibet Railway. From Xining (the provincial capital, on the main Lanzhou network) the run is around twelve hours; from Lhasa the journey takes roughly the same. Trains coming from Beijing, Shanghai, and Chengdu all pass through Golmud on the way to Lhasa.
By air. Golmud Airport (GOQ) handles a few daily flights to Xining and Xi'an, and a handful of seasonal routes to Chengdu and Lhasa. It is small and frequently weather-affected.
By road. Highway G6 (the Beijing–Kashgar national expressway) passes through Golmud. The G109, the old route to Lhasa, runs south across the plateau and is now mostly used by trucks; long-distance buses to Lhasa from Golmud have largely been replaced by the train. The drive from Xining is about a thousand kilometres.
Tibet permits. If you are continuing to Lhasa, you need both a Tibet Travel Permit (arranged through a Lhasa-based travel agency) and a separate Aliens' Travel Permit issued by the PSB in Golmud. Tickets onward cannot be bought without them.