I do all these jumps with a sniper or SMG for high mobility and I use MLC, so if you can't make these jumps with an LMG or AR, that is why.
Go to the NW corner of the map. You will see the green and rust containers. Climb the dumpster in the very NW corner where there is a hole in the fence to get through.
Climb through the hole. Crouch and walk up the broken piece of fence, stand when you make it under the top crossbar. Jump onto the top of the fence.
(On fence) Look west, there is an AC unit you can get on. Good view across the north, your southern side is blind.
(On fence or small cement divider below and east of fence) Jump to the white ledge or grey ledge next to a fire escape. Decent views, not easy to be seen.
(On fence) Face northish, jump onto rust-colored container. Face eastish, jump to the high fence by the army truck, aim for the end of the fence by the pole (fairly hard, long jump). Walk east to corner (on high fence), walk south to corner, jump onto the awning above the dumpster. You actually go through the roof of the awning and can lay under that roof and watch that corner (this often is a front-line battle here).
Go to the start point in NW. Walk south toward the 'patio' area 1 story above you (with the TV antennas and water tank). Climb the brown boxes to get up on that area. Walk to the western side by the white box with the antenna and sandbags next to it.
Climb onto the sandbags by the eastern edge of the white box. Climb onto the box. Carefully make your way around the antenna to the northern edge of the white box (don't fall off), face east.
Jump onto the lower part of the antenna in front of you (it is easy to fall off of the box or hit the center piece of the antenna, be careful).
Once on the lower part of the antenna, face south and jump onto the higher part of the antenna. Get on the center pole of the antenna and face south (you are looking at a fire escape with sandbags and a camera/tripod).
Back up to the north as much as you can without falling off. Do a short run and jump to the fire escape.
Hide behind the sand bags or jump up to the 5th step of the ladder that is in the fire escape (this makes you less viewable from below).
Also you can jump from the fire escape to an AC unit next to it (not great).
From the box by the antennas, face north and jump to the metal thing with the 'grand opening' banner.
Get on the string of the banner (left side-looking at banner) and jump up onto an AC unit there.
[more cheats for Call of Duty: Modern Warfare 2 here]