WATCH_DOGS

Overview
This is a story related achievement and consists of 6 missions, all of which take place in the Pawnee area (in the North West of the map) and are reasonably straightforward. The missions are:

1 - Hope is a Sad Thing
2 - A Pit of Paranoia
3 - Unstoppable Force
4 - The Future is in Blume
5 - For The Portfolio
6 - By Any Means Necessary

Serious Glitches
The main reason for this guide is to warn you about a pretty serious glitch in the 5th mission 'For The Portfolio'.

There will come a time when you need to protect T-Bone in the scrap yard however, even after you've killed all enemies the game will keep the 'Protect T-Bone' state and not let you progress with the 'Regroup with T-Bone' objective.

This happened to me 3 times as I progressed through the mission. The first two times I was able to just 'Load Last Autosave'. However, on the third time that trick wouldn't work.

With a bit of research I found the link below:

http://forums.ubi.com/showthread.php/883452-Story-Mission-Gl...

Basically, you need to:

Press the Xbox Home button.
Press the start button.
Select 'Quit' to close down Watch Dogs on your console.
Switch off your Xbox One.
Restart it.
Start up Watchdogs
Select 'Continue' on the main menu.

This will put you back into the 'For The Portfolio' mission and will correct the 'Protect/Re-Group' issue once you've killed the enemies again.

I hope this helps anyone who gets stuck!

Useful Walkthrough Videos
Finally, IGN has put a very helpful series of gameplay videos on youtube: