Astronauts undergo many hours of training to familiarize themselves with the exact route they will have to take once out of the space station.
A spacewalk may be either tethered- the astronaut is connected to the spacecraft- or untethered. (Untethered spacewalks were performed only on three missions in 1984 using the Manned Manoeuvring Unit (MMU).)
Astronauts use tethers to remain attached to the space station. They also use tethers to keep tools from floating away. What if they get untethered by accident? NASA spacesuits have mini-jet packs which enable the spacewalker to float back into the station.
Picture Credit : Google