Overturning analysis could apply to many different configurations or structural systems. You will need to be a bit more specific.
But in general the most important thing to understand about how the load combinations play into overturning analysis is that the combination factor for vertical loads plays an important role in the overturning result.
For example if you have a shearwall and you are looking to design the Tension side hold down:
The load combination with the least gravity load should be used. For example 0.6D + 0.7E. You must recognize that the Dead load forces in this calculation act to resist overturning. In otherwords, you use the least Dead Load to get the Highest Tension force.
Now on the other side of the shearwall you have a compression chord. For this side you use the load combination with the greatest vertical contribution, recognizing that this vertical force adds to the compression chord force. For example 1.0D + 0.7E.
So you use the load combination that causes the most critical effect on the element in question. This is true for all structural elements, but can be a bit trickeir with overturning because you have loading in different directions that are being considered simultaneously.
