What types of maneuvers increase the load factor on the aircraft?
The load factor of an aircraft is given as the ratio of lift to weight. 

i.e. $n = \frac{L}{W}$

So, an maneuver that changes any of these two forces acting on the aircraft causes a change in the load factor. Usually, it is the lift which is considered the variable.

Consider an aircraft in a level turn. In addition to the lift and weight, the aircraft experiences centrifugal force, which is counteracted b the horizontal component of the lift.

 
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For a bank angle of $\theta$, it can be shown that the load factor can be given as,

$n = \frac{1}{cos\theta}$

So, as the bank becomes 'tighter', the load factor increases. A load factor greater than one will cause the stall speed to increase by the square of the load factor.

Basically, as the load factor is increased, the aircraft minimum speed should be increased to prevent stall. 

For aircrafts in steady climb, the principle is essentially the same.


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Here, the weight is less than the lift and as such, the load factor is (slightly) less than one. 

As the aircraft stalls in level flight or unaccelerated straight climb, the lift becomes zeros and the load factor also becomes zero.