Mission 03: Collateral
After the cut-scene events, you will need to rescue Clara with a well placed shot. Pop the guy's head and follow Clara outside (automatic focus should make the shot quite easy).
Objective: Defend Clara from the attackers
You know when a game has good ally AI? When they don't rush forwards and get shot to pieces when you are trying to protect them. Thankfully, Clara has good AI and will wait for you to clear the area ahead before moving up. Aiden will need to work his way around the L shaped balcony to reach the stairs on the far side. Clara should stay in cover most of the time and as long as no enemy reaches her physically she should take care of herself.
Move forwards using the small wall on the right as cover (you can also smash the decorations (red brick diamonds) if they are obscuring your shots. Deal with the roof snipers first and then the enemies coming along the balcony. After rounding the corner and mopping up the enemies on this level, enemy reinforcements will arrive in the parking lot below.
A well placed grenade or shots will finish them off quickly. Be careful about using the wooden sections of the wall for cover as it will break after a few shots and bullets will begin hitting Aiden. Once the parking lot is clear, head for the stairs down and a new objective will pop up.
Objective: Escort Clara to her car
Cross the parking lot towards the marker on the opposite side (picking up any guns or ammo you need). As Aiden approaches the small hall leading to the marker, more enemy dots will appear on the map. Enemy cars will arrive (one at the parking lot, one in the nearby alley). Use a grenade or assault rifle to take out the parking lot car (as there is little cover here and they pose a large threat). Then pick off the enemies arriving via the alley until the map is clear once more. Walk Clara to her car in the alley and another objective will show up.
Objective: Escape the motel area
Time for another car chase, or not. Two goons will appear at the end of the alley. Shoot them. That's it. Run towards the edge of the search area (no reinforcements should appear) and you should be good to go.