Whip out your phone, select Stubbs and select job and you'll be able to complete 5 mini-missions for him.
Stubbs wants you to kill one of his politician friends at the Superstar cafe.
Make your way to the cafe, go inside it, and listen to the crap that the target is saying. Once he's shut up, put a bullet in his head. Be careful though because there are three or four body guards inside the cafe who will shoot at you once you've killed him. You'll have to quickly turn around and take them out, and maybe one more guard outside, then drive a few blocks away.
Knowing Me, Knowing You
Stubbs wants you to steal Bryce Dawkins car and get it fitted with a bug. He says you might have to go off radar to get it done.
Grab a vehicle and make your way to Bryce's house where you'll find a nice shiny orange Infernus. Get in it, and drive it to the complete opposite end of Alderney where you'll be able to get it fitted with a bug. If you damage it, it's ok, the bugger (haha) will fix it for you.
Once it's been bugged, you'll have about 3 or 4 real minutes to get it back. This time, though, you can't scratch the car or Bryce will know something's up. Every time you get a message telling you what time the vehicle has to be back, it means you've got a minute less real time.
Drop it off at his house, then move about a block away.
At some point after the mission you'll receive a text message giving you a number to call if you want to listen into the bug in Bryce's car. I suggest giving it a call and listening to random stuff like Florian singing "living my life like it's golden" and shouting at traffic.
When The Blue Chips Are Down
Stubbs wants you to rescue a CEO of a company who has been earning a bit more money than she should have.
Grab a vehicle and get to the CEO. The police have blocked off all of the alleyway entrances and exits, so you'll have to kill all of the cops and fight your way into the alley.
Once you get inside, kill all of the cops near-by, then stand behind the CEO and uncuff her. Once she's free, she'll get in the car, so get in it with her and drive out of the alleyway.
You'll be told to take her to the helipad above the Booth Tunnel, so make your way there. Once you get there, you'll have to defend the helicopter from the attackers, although it only takes her about 5 seconds to take off so you should be fine.
She'll fly out to sea and get on her yacht.
Stubbs wants you to snap a photo of a fellow politician picking up prostitutes.
Grab a vehicle and get to the alley near the red light district. Once you arrive, you'll be told to get up to the roof for a good view. Head into the alley and up the steps, then climb on the wooden box and pull yourself up onto the roof. Stand in the mission marker and Johnny will call Stubbs. He tells you that the person he wants you to photograph is driving a red Cognoscenti.
After a minute or so, the politician will arrive. Wait until the hooker is talking to him, then snap a photo. If you did it right, you'll be able to send it to Stubbs. After a short while, the car will drive off and you'll receive your payment.
Stubbs needs you to take out someone who is going to talk to the press about sensitive information.
You'll have about a minute and a half to reach the destination, wherever he is, so quickly make your way there. Once you arrive, he'll tell you that you're going down for a long time and try to escape.
Simply speed after him and shoot him through the window or blow his car up. Once he's dead, you're done.