I am currently working with a lot of points of which every point has to be labeled.
I am already using the "Easy Custom Labeling" tool to move the labels and create lines to connect points with labels, as soon as there is not enough space for the labels.
Now I have different problems:
It takes a lot of work to align the labels manually to reach the goal to label every feature. Is there a faster way to to it? Very often, I let one label disappear, as soon as I move another. I think in ArcGIS there was the option to convert labels to annotations and then align these annotations very close to each other. The labels in QGIS disappear as soon as they are to close together.
As soon as I go to the Composer Manager, some labels arrange differently although I choose the same scale as I used when moving the labels manually. This means that I have to arrange the labels manually in my data view, switch to the Composer Manager and refresh the Map to see, whether it finally worked. This process takes even more time.
I am happy for every hint to label more effectively!
Some maps have a much higher density of points, I just started with Italy.
On the 'Advanced' tab of the 'Layer Labeling settings' menu there is the 'Engine setting' button. If you open that dialogue, you will see the option to show all labels, including colliding labels. That should give you more control and a more consistent behavior.
Something I used to do previously when I had similar problems with label placements is to create centroids of the polygons (vector - geometry tools), label those using the option to label over point and then move the points around to ensure perfect placement of your labels.