I'm not sure but I think I've seen a post about converting particles coordinates to nulls. Whether actually someone posted something like that or not, I was wondering if there's a way to grab vertex coordinates from a pointcloud and convert them to nulls objects. At that point I could export nulls to AE to add text in post or add more stuff with Plexus.
Is this possible?

Probably not exactly what you're looking for, but over at the Area there's a Python script called ICE Track Particles (login required) by Julian Johnson...

Thank you Hirazi Blue,

now I'm trying to figure out how to tag particles. I'm looking on the user guide as well, but I haven't found anything so far.

Particles are akin to vertices, so you tag them by pressing T and selecting them.

Thank you Chris_TC, it works fine
I just have to watch out to the number of particles to nulls as the viewport may become quite slow, but I need just a few of them.

Yeah, it's slow. The fastest method is to use Guil's Transform Objects by Particles command (ICE -> Kinematics/Effects), but you have to select objects for constrain and then you have to manually pick a point cloud, change index each of the nulls... It's not so fast to setup. So I rewrote command for myself: basically you need copy ConstraintToParticlesExtended.py plugin to your \Autodesk\Softimage_2012_SP1\Application\Plugins user folder and then you can select multiple clouds/meshes/curve points and run InstantiateNulls.py script to get result that you looking for.

Thank you iamVFX.
As you said I've copied the scripts in the user folder:
\Autodesk\Softimage_2012_SP1\Application\Plugins\InstantiateNulls.py
\Autodesk\Softimage_2012_SP1\Application\Plugins\ConstraintToParticlesExtended.py

but I don't know where to look for those scripts in SI.

So, I opened the Script Editor, loaded the InstantiateNulls, selected the point cloud and then launched the script. At that point the point cloud is deselected but nothing else happens. I've tried with a curve too, but no luck. Am I doing something wrong? Sorry for these basic questions...

InstantiateNulls.py is a script for button, but yes, it's also can be runned through the Script Editor, and there is no need to place it into the plugins folder (unless you wanted to). It's works with selected points only. If you want to create nulls for every point in a point cloud just select them all (Ctrl + A by default) and run the script

It works, thanks iamVFX