what your question is regarding. If you're referring to the multiplayer, there are a
variety of approaches you can take.

Scavenger: A perk that allows you to pick up enemy book-bags that replenish your
ammunition as well as grenades.

Dual mags: These are very helpful as it starts you off with --/150 ammo. The bonus to this
attachment would be that it creates faster reloading (kind of like Sleight of Hand).

Now if you were speaking upon campaign, then I'm afraid I can't help you out with that.
However, I'm sure there's an answer for that around this site. Just browse around. (:

It says glitch so im thinking ur referring to zombies just dont glitch and use the box
between rounds whn ur outta ammo

scavenger pro is the perk to help u get replenish more ammo

What ammo like gun ammo, genaides. If gun ammo in zombies u shoot all the places where you
can get all the gun in the room where u first land in and only use 10 bullents per gun u
can get and yeah you get 1000 ammo true. If on online dont know. If genaides use scavenger
make it pro and it will replenish more ammo found in dead body on the ground (just t-bag
them :)... Lol) it works to me and i use it in the ps3.