What do you think should be done to prevent copyright violations?
There are three main categories of copyright violation, each best handled in its own way.
Large-scale commercial infringement, such as sites allowing download of current movies, is too big of a money-maker to convince people to voluntarily stop. In this case, civil and criminal prosecution may be the only way to prevent it.
Individuals participating in P2P sharing networks are often doing so because it's easier, cheaper, and more convenient than getting the same materials legally. The best prevention here would be to work to create legal channels with the same flexibility. Note that illegal sharing of music dropped off significantly when iTunes became prevalent.
Individuals unaware that their activities are infringing may simply need to be educated about how copyright affects them. Both the economic impact and moral issues can be used to explain how infringement hurts artists.
At the moment, rightsholders tend to try to lump all three groups into one pile and treat them the same way, even though this has been proven not to work (DRM is an example of this). They need to acknowledge the differences between mass infringement and a kid with a flash drive.
The exact method depends on where you are. In the US, publication with a copyright notice (which can be as simple as "Copyright (C) 2011 by O. G. Whattaschnozzle, all rights reserved" ... though you should use the actual year you published it and your own name instead of OG's) is considered to constitute copyright. If you really think your song has commercial potential, you should get your copyright registered, but this involves some expense.
Personally? I think the creator of a work should receive certain exclusive rights to that work, for a certain amount of time. I happen to think that amount of time should be rolled back appreciably, perhaps to 50 years after the work is made available. I think there should be exceptions for orphan works, standardized agreements, statutory fees, and a centralized database, but that's even less likely.
No. Unless things have changed, the most accepted form of not breaking copyright with printed material is that up to 1 third of the material may be copied for reference purposes. Any more then that is breach of copyright. Why do you think it's called "Copyright" if any one is allowed to copy it entirely? The "right" to copy it remains with the copyright holder.