My biggest tip is this... When you get to the second large room, where you can pick up the sniper rifle with scope (one in the stairs up, more leaning against the balcony rails), load it up and hang onto it for the last (roof) part. Sure, pick off a few guys (flamethrowers are great targets since they explode and kill others), but take at least 25 rounds (more is better) to the roof. Maybe you pick up more along the way, but the rifle saved my bacon on the roof.
OK, other tips: First big room: Take out the guy on the balcony to the left, then make a mad dash (push down on left stick) to the right. You can take a quick breather behind the downed column (go prone), but the idea is to get to the corner that separates the room you enter with the room to the right. There is a great corner to hide in L-shaped column, don't go into the next room just yet). From here you can rifle a couple guys in the next room, then dash behind a crate. From here, get the guys under the scaffolding (turn left) before storming the next room.
From here on, it's pretty straightforward, until you get to the roof.
First thing I did was snipe the guy with the panzerschreck (upper left balcony).
Then the obvious guy across the way and to the left.
Now I just snipped the other 2 or 3 guys that hide across the way.
Once they are down, you need to move to the left.
Try to snipe the guys behind the next crates (use tight corners to shoot them in the arms for a one-shot kill).
You eventually get the 3 or 4 guys down.
The rooms to the left are straightforward too.
Once it's clear, it's back to the main path.
Once you are back out in the open, there's another guy with a panzerschreck (up and to left). Take him out first (you should be hiding behind the barricade, not the sandbags).
Now snipe as many others as you can and the level should open up.