When you get in the truck then get out know out the real gaurd snipe the dog and kill the terrorist there is a door by a car. Open it. There are diversion cameras ring airfoil rounds and sticky shockers. If you go to the back of the room there is a dead gaurd behind the cones.

I don't know if any of you have heard of the teleport glitch, but most of these revolve around that.
To use the teleport glitch, you need to find a pole that will let you swing left 180 degrees.
The only ones I have found are in the warhouse and in federal bank, where these glitches are found.

In the WAREHOUSE

You can teleport to the center of the map, by climbing up the pole in the spy respawn, and flicking left. At the same time, click B.
This should take you to the middle of the map on the ground floor by some crates if you have completed correctly.

It is important that you do not jump, because this leads to another glitch. If you jump before doing the teleport, you get taken to where you jumped. So in effect, after you are out in the map, you can jump wherever you want!!!

You can also get into sector 3 before it has been unlocked. This is quite complicated and you need a partner.
When you are in the spy spawn, to your right, near the wall, is a gate leading to sector 3. This is locked until you hack sector 2. To get over it, stand just to the right as you face it, and start to back flip off the wall.
Position your mate on the crate further to your right, and get him to jump on your head as you start to flip. He should then jump off your head, towards the ledge over the entrance to sector 1. Then do the same thing again, only closer to the gate, and your mate should pop over!!!

In the FEDERAL BANK

You can teleport to 2 useful places.

The first is on top of the chandelier. In the spawn, there is a ladder and a pole. Jump down staright over the ladder. DONT TOUCH IT!!! You lose half your health, but it is worth it. Then climb up the pole to your rightand teleport onto the chandelier in the lobby of the bank!!!

Second, you can teleport to the vault. When you get off the ladder, to your left there is a vent normally used to reach the vault room. Instead, run to the right, and backflip off the wall, so your feet hit the exit sign. Then go to the same pole as above, and teleport, you end up in a very glitchy place above the map. Do not panic. Straight in front of you is a lift shaft that you just hop down.

Warning! These glitches can be used to cheat and gain ranking points. Please do not, as that is against the idea of the game.

These cheats thanks to

SquealerUK
galaxy cruncher