Head over to a TW@ Internet Café and log on a terminal. Use the internet to find the ad for Goldberg's lawyer firm. When on the website, spent a little time reading Niko's funny resume, then send it to the company. You will have the number to the company on your Cell Phone when you are done. Leave the cafe and now you must wait until one of the lawyers call.
Soon the lawyers will call for an appointment. Get yourself a nice suit and smart shoes from your penthouse or from Perseus. Strangely enough, the mission won't start if you are wearing anything on your head at all (which includes glasses, hats, and even a balaclava). You may have as much as 24 hours game time to kill before the interview; the usual between-mission activities can be undertaken so long as they don't overlap the appointment time.
An hour or two before the appointment time, head over to Tom Goldberg's workplace, the icon for which will now appear on the map. Enter without a weapon drawn and don't attack anyone. Walk to the receptionist's desk and she will call Goldberg to find out if he's available.
Follow the receptionist to Tom's office and watch the short cutscene. After that, listen to some interesting lines and when you're ready, stand up. Be careful that you do not wait too long to stand up, since Goldberg eventually will respond to Niko's awkward answers and non responsive attitude by calling security, which will force you to fight your way out. Take out your weapon and point it at Goldberg. After he says where the files are, retreive them and then push him over to the window. Point your weapon at Goldberg's head and shoot him out of the window for a pretty nice killing.
An easier way to kill Goldberg which will leave you with no wanted level is to stealth kill him with a knife. Slash his upper body to kill him. Then knife the window without curtains to break it. Jump out of it and steal a getaway car.
There is also the hard way of simply busting your way out with firepower. At any time during the interview, stand up and equip a weapon, and simply shoot him straight in the head. Grab the files left in the office. Once the receptionist comes in screaming, grab an Assault Rifle or a Carbine Rifle if you have it. If not, a shotgun is pretty good at times, but lacks long range ability. Blast your way out of Goldberg's office and move to the lobby. The guards will have covered the door to the office, and they are now swarming the area. A 3-star or a 2-star wanted level (usually a 2-star on the PS3 version) will now appear. Shoot the guard at the top of the stairs and he will fall down in a very bloody way down those steps. The top door is locked, so you will have to make your way 2 floors down to get out. Try not to shoot the cops, or else the NOOSE team and rarely the FIB will be involved, and you'll receive a 3-star (or higher) wanted level, making the escape harder. Once outside, grab a fast vehicle and evade the cops. A fast car should be used since the cops have a lot of vehicles being deployed. A parked sport car, such as the Comet, or even stealing a police car makes everything a lot easier.
A safer, though potentially longer method is in using the nearby subway. Enter the tunnel by the law offices and board a train. It will take you out of range and "lose" your wanted level.
If you miss the interview for any reason, it will be rescheduled for six hours later.