I thought I'd just put up six quick tips to help people survive ctOS Chicago in Watch Dogs.
1 - "Open your World"
Lots of your cooler and more useful skills will be locked until you complete the act one mission with this name, so unlike the Assassin's Creed series where you probably should do all the side stuff as soon as it becomes available, just power through the main story until you get to it (it's near the start) before doing any of the side missions.
2 - Silence is Golden
You can almost clear out an entire gang base if you use your silenced equipment (which mostly means the starter pistol at the beginning) and aim for the head, which always nets a kill unless you are shooting someone with a helmet. Civilians also have less chance to call the cops since they don't hear gunfire (unless you keep missing). Use focus once you've unlocked it to help steady your aim.
3 - The Destroyer of Criminal Convoys
Once you do enough criminal convoys (10 I think) you get to unlock this rifle (called "The Destroyer"). Choose those first 10 missions wisely as some are much harder than others but once this gun is in your hands none should pose a problem. One hit from a rifle disables a vehicle and since NPCs NEVER get into a car that they didn't start with it makes all the chase x person tasks much easier as you can force your prey to be on foot. A head shot from this will also kill the heavily armored guys, just aim for the goggle section. Once again, focus is your friend.
4 - Bad boys go to the beach, and sleep in their cars
The Chicago police are ridiculously aggressive, willing to kill bystanders to get to you. While unlocking your magical phone abilities to use the city infrastructure against them is certainly a good way to slow them down, an easier method is to head for the nearest marina and catch a boat since they are incredibly allergic to water and will not chase you there. The helicopters will, but your magic phone can disable them. And if they have snipers well, bullets (especially from the Destroyer) can help with that. If there are no boats nearby a good alternative is to use a blackout doohickey (or cause one the old fashioned way) then hide in your car, especially if you have the related bonus skill. I've managed to hide in the middle of a freeway, with a police cruiser right beside me. It looked at my smoking wreck of a vehicle for a bit then drove off. :P
5 - "Steal a Vehicle" contracts need Skill
The "steal a vehicle" fixer contracts were the hardest ones in the game for me, since you can't really get out of the car for longer than 20 seconds. You'll definitely want as many/all of your skills unlocked before attempting them, along with pockets full of consumable items. Being familiar with how various vehicles handle and the various short cuts and back road ramps as a player is also handy.
6 - Be Crafty
Crafting stuff is great, but since its a pain to go buy equipment or collect them it might help to know what stuff is used most (or at least, what stuff I used most). The number one item is: Jam Communications, followed by Blackout, followed by Focus pills. Frags and IEDs had some rare moments, mostly during campaign missions but I didn't really use any of the others so unless your play style widely varies from mine, save your resources! I found lures to be especially useless, but perhaps have some value to those who want a "no kill" play through (yeah, good luck with that).
That's it, hopefully it's of use to someone out there! :)