I think passion plays a huge role in the manifestation process. When we want something passionately, there is usually great intensity behind our emotions and feelings and therein lies the key. When our feelings behind a subject are intense, the physical manifestation of that will move into our reality quicker, as opposed to those thoughts that come and go without any real emotion behind them.

One thing to note is that the intensity of the emotion or feeling will speed up the manifestation process whether you are feeling good or feeling bad - if we have thoughts on things we don't want, we have to be careful not to add any intensity of emotion or feeling to it because by doing so, we are actually inviting it into our reality.

We're always manifesting at some level but most of us do it unconsciously and blame everyone but ourselves for our current state of affairs. When we begin to apply the LOA consciously and find things to be passionate about, our manifestations and current reality begin to change accordingly.

When you open your eyes do you see reality?

if you do, it is the physical counterpart of your consciousness that you see.

that is your manifestation.

Examine the contents of your consciousness right now.

What's in your mind is what is accepted by you as existing physically.

Change you mind and you will start to notice different things that you didn't notice before.

this change is your new reality or new manifestation.

are you the YOU that is manifesting this?

Yes!

How?

Because You and I and them are all the same person, called creation.

Passion as Michaela explained in her excellent answer as intensity is the effect that enhances the default cause & effect relationship of thought and physical reality.