Different levels have different strategies...
Level: Boss
Equip the Pudge Ragdoll, fully upgrade the multiplier (in Upgrades), add bigger basket to the Treasure chest, add Vacuum basket to the treasure chest, and shoot, add bigger basket to the Treasure chest, add Vacuum basket to the treasure chest, and shoot, and so on... this give a bunch of points. it does not require the Pudge Ragdoll, but is most effective with it.
I would like to add in the above strategy, that by using a grenade to blow up the aquarium, then bringing the multiplier to x6, equipping the Pudge ragdoll,and equipping every shot the basket vaccum, you can earn a net of 210 paper points every shot, as the Pudge ragdoll gives 360 pp, and the vaccum costs 150 pp.
Level: Warehouse
Equip the grenade (required) and blow up the left side row of boxes. in doing so, this will reveal a secret basket, that gives out 15 paper points as opposed to only 10. You can use the same procedures as the ones above (Equip the Pudge Ragdoll, fully upgrade the multiplier (in Upgrades), add bigger basket to the secret basket, add Vacuum basket to the secret basket, and shoot, add bigger basket to the secret basket, add Vacuum basket to the secret basket, and shoot, and so on... only after the secret basket is revealed). This also brings in lots of cash.
*Note: The treasure chest in boss, earns MORE cash than the secret basket, but takes LESS skill to earn. for more skilled players, i would suggest (2442cc, the founder) to go for the warehouse level.
More strategy coming soon!