How to change button for start next wave in MW3 survival mode

Survival mode never ends. I have found the best strategy thus far is pick an area you can defend easily next to 1-2 buy points, preferably ammo and grenades crates.

It needs to be an area with overhead cover to avoid choppers, ideally should only have 2 entrances at most. I have yet to find a good spot on maps that have 1 entry point.

Get the sentry granade launcher, have your partner do the same, Get Riot Squad reinforcements,

The idea is you can stay behind the sentry guns and riot troops and kill everything, You have Sentries guarding 1 entrance and the riot troops at another.

You will need explosives later on to take out juggernauts, normal enemies will start to take a whole clip to kill around lvl 30 if you dont got for headshots.

C4 and Claymores are helpful but can get a little expensive to buy every round.

Flashbangs are invaluable for taking the juggernauts out. By mid lvl 30's you facing 4 juggernauts, and exploding dogs with armor on most maps. It can get crazy. I have not found any strategy of displacing to be effective, the enemy troops will claymore most doorways and choke points.

Perks - Longer Sprint was the most helpful I found.

Grenade launchers ('noob toobs'), sniper rifles, C4, and other explosives are all pretty useful, but what you need the most is time.

If you can find a place where you can see them at a range, or you can glitch them into staying away from you, you'll survive a lot longer. I've killed quite a few juggernauts in co-op with a friend, and usually I'd be the 'bait' while he laid down somewhere out of the way with a sniper rifle and laid into them. When I could I'd find a place to hide and shoot them with explosive weapons, or, in a pinch, an LMG.

There are some areas where you can let your friend 'die' and they will keep the juggernauts busy while you kill them. The most popular is to block a doorway with your co-op buddy's downed body. You have to revive the buddy every so often so that you don't lose the match, however.

In Modern Warfare 2, I also found that juggernauts would freeze if they were unable to path to me - hiding under a table helped, for instance. They'd just stand there, unable to determine how to get to me, and I'd snipe them in the head over and over again.

If co-op "cheesing" them isn't an option, and/or you've got cash to burn, there are a few weapons and special items that can help:

• Sentry guns can do good damage to Juggernauts, although they will destroy them quickly if left undefended. They also take a good long time to get spun up, and won't even try to lock onto a target if you're standing in an area anywhere between the gun and the target. On a Juggernaut round, I'll tend to move my gun to a position where it has a long line of sight on the enemy, and I'm standing closer to him than the gun is.
• Predator missiles and air strikes can quickly kill a single Juggernaut, or perhaps a couple if they're bunched together.
• Riot shield teams are moderately effective against Juggernauts. You may lose a couple, but if all four are focusing fire, they can take down one on their own most of the time. If you're supporting them, (or a sentry is) you can often get away with fewer losses.
• Items that increase your survivability (auto revive/body armor) are obviously helpful.

Flash grenades are the surprise winners here - they can stun a Juggernaut (and in the riot shielder's case, cause him to drop his defenses) so that you can go for headshots without taking damage. Also, since the Juggernaut(s) aren't firing, the effectiveness of your other items is also increased. The only downside is that their head tends to move while they're stunned, making headshots harder.