Hello,
I downloaded four meshes but I can’t rig them because I don’t have enough experience in rigging. Can someone rig them please? The file is uploaded here: http://www.pasteall.org/blend/41529
Does that have to be exactly that model?
I’m pretty sure you can find similar models already rigged out there. Even generating with MakeHuman or Manuel Bastioni lab addon.
Yes because they are more detailed than the ones that can be made with MakeHuman or the ones that were rigged. 
The problem with those models is that they are not in ideal positions ea T shape.
Thy could still be rigified, however then its a lot more work, and it most likely will not be ideal.
Imagine 2 differen hand shapes, and the rigger has to place the bones at the exact same locations, near to impossible.
So i dont know how you got these model but maybe your able to scan someone with a T pose ?
If its just the head that you like, you might also use makehuman and transfer the mesh head using blender. and get a T pose from makehuman. (btw there is now an addon for blender to to make “makehuman alike, but better” models inside blender directly.
Another idea would be to use Daz3d. They have some great models with several shaping addons.
If, I was going to rig these, I would suggest deleting one side of the model so at least they would be symmetrical, I want to say they are a daz studio export but don’t quote me on that.
hm in this case, the models pose in such away that even a half model doesnt do the trick, they are turned and bended over their central mid axes. So i dont know how you got them, but try to pose them first in a T pose, its a lot easier to rig them then.
Looking at the models, they have indeed high poly count but maybe that’s not all there is.
Some models are lower count, but bend better, you should take a look at these models : http://www.manuelbastioni.com/gallery.php
They bend better then the models you showed here, and they dont contain wrong meshes (like leg surface cuts inside your model).
Whats more that addon will allow you to change character types, facial expressions and figure type with many real human alike shapes (fat thin peer etc) and anime chars. The models have an option for subdiv (its a button) for even better shapes but keeping a more correct mesh layout.
These are a better (visual) quality than Makehuman and while they’re similar to Daz’s Genesis(s) it seems to have too many poles/triangles or loops that aren’t as clean as Genesis, so I don’t really think it’s from them.
But yeah, these are definitely a poor choice to rig considering the look or uniqueness with them; I suggest using Daz3D/Genesis as you can export it with UVs/Textures and rigging plus it’s cleaner and you can get a lot of premade customization options for them.
If you’re dead set on getting these rigged, I recommend using Blenrig; you essentially just fit the premade rig, and a blob mesh if you don’t want to weight paint, to the mesh then when you’re done, you can pose it with the rig.
If you want, I renamed the bones for a similar process with Daz3D models so that I could use it’s advanced rig options on them while maintaining the original vertex weights, and I could give you the rig for use.