You might know that all matter is made up out of atoms. Now, atoms themselves have a core, or nucleus, and electrons orbiting around the nucleus. The core has positive charge, the electrons have negative charge.
When you are rubbing the glass rod with the silk cloth, electrons are stripped away from the atoms in the glass and transferred to the silk cloth. This leaves the glass rod with more positive than negative charge, so you get a net positive charge.
Why do the electrons go from glass to silk and not from silk to glass? That depends a lot on the minute details of the material. Ultimately, for every two materials there is one of them where electrons are happier. It just turns out that for glass and silk, electrons are happier at the silk cloth.
Now to your second question. Here, the important thing to note is that in your typical solid material, the positive charges, which are the cores of the atoms, cannot move around much. They are locked into a rigid structure. The tiny electrons, however, can move around much better. That's why the glass rod can induce a net negative charge at one end of the paper clips.
EDIT: Let me add that there should also be some attraction between the silk and a bunch of paper: The electrons in the paper will be pushed away by the electrons in the silk, leaving the end of the paper that is closer to the silk with a net positive charge that then gets attracted. However, it might very well be that in your silk cloth the electrons are overall too spread out to have a strong enough attractive effect.
Get together a collection of charges. As many different ways to generate a charge as you can think of. Go ahead and invite your friends so they can think of some more. (As a practical matter you make static charges just before you use them, but still...)
Now, test them pair wise to see if they attract or repel one-another. Keep careful records.
Find the largest set that are all mutually attractive and the largest set that are all mutually repulsive.
You'll find that the attractive set has exactly two members (though you can make many different examples of this set) and the repulsive set consists of half (either half!) the charges you've created.
Ponder that for a while. It also gives you the answer to how like charges respond to one another (though you can get that directly by preparing two similar charges).
Best Answer
Short answer:Finite size of dust particles and inverse square law.
The side of the dust particle towards the screen is negatively charged and the other side is positively charged.Now due to the inverse square law,the force of attraction is more than than the repulsion as the negative side is closer and the particle experiences a net force towards the screen.
Why the electrons don't travel to the screen?
Because they still tightly held by the atoms of the dust particle.The T.V. screen only induced a slight polarization of the dust particle.The electrons have not travelled to the negative side(unlike conductors) but the atom itself undergoes slight polarization.(Similar to what happens in dielectrics).