PAYDAY 2: "Walk Faster" Achievement
This one can be tricky at first if you haven't already played the heist. The layout is easy to getting used to, it's the different paths that may throw you off, so feel free to run around and restart a lot.
Once you get the general feel for it, I recommend a a suit or a light vest and a saw, although I don't think the saw is absolutely necessary, an upgraded drill would probably work too, you'll just miss out on the extra 30-40 seconds of running around, but the saw is the best way to go.
Getting from Floor 2 to Floor 3 is probably the more tricky ones as you don't take the stairs, you have to use a ramp of debris.
Ignore most enemies, if they get in your way or a crowd forms in the middle of a hallway, you might want to take a few out if you don't have the appropriate health/shield/dodge skills.
WATCH OUT FOR TRIP MINES! If you are shooting to open a door from inside a room, make sure you look down at the door frame to see if there is a mine!