where are u guys playing tonite? hehehe...

if you havent already, play hardcore mode.
more teamwork, and lesser ppl rushing everywhere since you die easier.

You should try watching Shooter. Movie gimmicks and tricks aside, you could barely see the sniper in the movie. And watch Discovery channel too. See how the Royal Marines train their snipers.

Does anyone know where to find this intel ?

23 - Act II One Shot, One Kill - Carry the allied NPC "McMillian" to the
Pripyat ferris wheel but do not place him on the highlighted spot on the hill yet; you need to scout around this area so you know where to go once enemies appear and general mayhem occurs. Put the ferris wheel behind your character and look for a side street towards the southeast (use your HUD compass). There should be a non-descript (closed) door to a sad looking Communist Russian apartment building. This door will open later during the firefight (enemies are spawned from there). Place the allied NPC at the spot on the hill and prepare for hordes of enemies. Once enemy choppers appear to fast-rope troops, the aforementioned door will be open. Head into that room now and grab the intel on the floor. If you are having difficulty grabbing this intel, you can always stage select and use the easiest (Recruit) difficulty to survive the enemy onslaught.

I can't find the mentioned "room" in that level. 

What is the purpose of the intel?
In my first round of COD4 (beginner mode), I didn't get any intel, only at second round, so far only get 4 intels