KL's rail network covers most of what travellers care about. The LRT (Light Rail Transit) runs on two lines through the centre; the MRT added two cross-town lines that connect Bukit Bintang, KLCC, and the suburbs; the Monorail loops through Chinatown, Bukit Bintang, and the Golden Triangle. A single rechargeable Touch 'n Go card works on all of them and the KTM Komuter commuter trains as well. Stations are well marked in English.
Grab (the local Uber equivalent) is cheap, reliable, and the easiest way to cover the gaps the rail network leaves — many of the bigger malls, embassies, and residential neighbourhoods are not within easy walking distance of a station. Allow extra time at rush hours (5-7 pm); KL traffic is notorious. Walking around the colonial core and KLCC is fine but pavements are uneven and the heat punishing — most locals take taxis even for short hops.