Okay, the number of requests for this is getting ridiculous...
Here's a tutorial.
Requirements :
1. Brain.
2. Modem.
First, make a private room.
Then, unplug the internet wire from your modem.
After that, change the game mode to Capture the Flag (CTF)
Then, change the kills to 140(If you have vista, 130, or you get D/C)
Next, get a friend to join the room.
After that, start the game.
Then, kill your friend ONCE take the flag and take it to your base.
Next, your friend leaves the room.
Then, you will get 1k exp and 2k money (or around that) each time.
Now you can repeat this over and over and switch places with your friend.
***Speed Powerleveling***
Here's a way to make it go a lot faster.
1. Open up HS bypass & combat arms and all that.
2. Get your CE or MHS open and go into the Shop ingame.
3. Go buy the lightweight vest thingy.
4. Scan for 10 in unsigned long in MHS (or scan 10 in 4 bytes for CE)
5. Take the vest off. Scan for 0 unsigned long MHS, 0 in 4 bytes for CE.
6. Put the vest back, repeat step 4.
7. Take if off, repeat step 5.
You should have 1 or 2 addresses...
Add them to your list and change it to something higher, anything you wish above 20 is fine.
You SHOULD be faster. Now you can run and get the flag easier & quicker.
Note : The speed powerleveling has not been tested. I just remember being able to edit slots of the backpack, so you can probably edit the speed of the vest too. There's no reason why it shouldn't work, unless they put serverside checks for it, which they haven't done yet.
Have fun!