Camping has many styles and each of them has to be dealt with in different ways.
Shield camping: This type of camping is less common in ONS, but I can imagine that everybody had experience to meet them as they usually appear on DM, TDM matches. Shield campers are camp with using a fully charged shieldgun, which can kill you in most cases immediately. These campers are usually located in corridors with one entrance where they can charge at the unaware players killing them. Dealing with them is a bit difficult as there aren't many weapons which can kill them without harming you. They should be taken out by weapons which can kill them immediately. If you have good aim then simply headshoot them, if not Flak Cannon is also a decent weapon against them. You can also give a try for Shield Gun. The Shield Gun can also kill them with one hit, if fully charged, but it is a bit difficult if you aren't used to the mechanism of the shield gun.
Sniper camping: Sniper campers are usually located on higher grounds where they can snipe out other players. If you are unlucky, then the map you play on also has the Super Shock Rifle which is a great friend of those who can aim well. Sniper campers can be taken out with well placed shots, if your aim is good enough. Shield Gun can provide defense against them and allows you to get near of them without dying. You can also backstab them with an ambush. Vehicles can also be threatening for them, because certain vehicles have splash damage and they also deal enough damage to kill them with one hit.
Hellbender camping: This type of camping has actually two subtypes: the one when you use the chain shockcombo gun and the one when you use the energy gun. The first subtype is usually done at corridors which are usually rather narrow, making the combos almost impossible to dodge. One shock combo can kill you, so you have to take it out without engaging it directly. The shock balls are also known for destroying rockets, flak shells and grenades, so you have to use a vehicle which deals splas damage. You can also sneak behind them, but the driver will usually spot you in time and s/he can kill you. The second subtype is usually done at higher grounds in a similar fashion as sniper camping. The energy gun is decimating against both infantry and vehicles. A fully charged energy gun deals 200 damage, which means that it can even take out Mantas with one shot. Like the first subtype, this type of camping makes the vehicle immobile making it a good target for rockets and link gun projectiles. Just don't try to get near to it, because the player can switch to the shock gun and kill you. The AVRiL is also an efficient weapon, because you can shoot it and then hide from the gun.
Goliath camping: This can be really nasty. The Goliath does splash damage and it also has a minigun which can take out players who can't be killed with the main weapon. Flying above them with a Cicada or Raptor and start shooting them will render the Goliath unable to defend itself and the minigun does poor damage against vehicles. You can also sneak up on it and start shooting it with a flak cannon or rocket launcher. The barrel of the Goliath turns rather slowly so it gives you time to evade the shot.
SPMA camping: SPMA drivers usually hide so it can be difficult to find them. The SPMA first shoots a beacon shell in the sky which allows the vehicle to shoot at targets which normally are impossible to do. Usually the vehicle is too far from you, so taking it out isn't really possible sometimes. The best thing you can do is shooting down the beacons before the SPMA could make another shot. This must be repeated, because the driver will attempt to make another beacon. If you are able to find the vehicle, then just simply destroy it.
Paladin camping: This type of camping is usually done at nodes, in narrow places and in corners. The Paladin's shield can even protect the vehicle from deemer strikes too. Taking them out can occasionally be very difficult. The best method is sending an AVRiL to the sky and then redirecting it to the vehicle. Never get too close to the Paladin, because it is able to kill you with its shield + primary weapon combo. You can also attempt to backstab the vehicle, but it isn't possible in every occassion. With your teammates you can take out its shield by shooting at it making the vehicle defenseless.
Leviathan camping: The Leviathan's deploy makes it an ion cannon, which can finish off most things with one shot. The Leviathan has 5000 hitpoints, which makes it be able to withstand multiple Deemer and Ion strikes. Fast vehicles and aerial vehicles have advantage over the Leviathan, because they can evade its rockets if the Leviathan undeploys and starts using its rocket launcher again. The Leviathan is a heavy hitter and should be attacked by more than one player.
This is still under construction, because these are the main types of camping which are the most common and I had in mind while writing it, but maybe there are other types of camping which I can encounter and write about them. If you need, I can extend this with custom vehicles.
