Start with the paperwork: the previous assessment and how its actions were closed out, floor plans, alarm and emergency lighting test records, fire door maintenance history, any alterations since the last inspection, and what you know about the people who use the building. For a residential building that includes the evacuation strategy and any occupants who would struggle to escape unaided. Records tell you where to look; a walk without them is guesswork dressed up as diligence.
The walk itself has to be methodical rather than casual: every space, from the top of the building to the bottom, looking for ignition sources, fuel and anything compromising the means of escape. Check door closers and seals, storage in corridors and cupboards, the state of any compartmentation you can see, and photograph as you go, because every finding you record later needs evidence behind it.