You may feel your local Wikimedia group has a full agenda. Wikimedia France also has lots of issues to deal with, and very little manpower. However, pardon my brusqueness, but I think that we have to set priorities and alterations to copyright law are a priority.
Many of the things that Wikimedia France does do not have a big impact. We get invited by various groups, universities, public institutions to give presentations about Wikipedia... and end up in a room with 20 people. Not a big impact compared to the amount of work invested, especially if you add travel time. During Fall, we realized we were spending lots of energy doing such kinds of things and we decided to limit the participation of board members to such events and solicit non-board members.
We get many requests from the press, and some are time-consuming. Again, it's worth prioritizing what's important or not, and adjust the quantity of work accordingly, It's not like PC Hebdo or Macintosh Monthly have an enormous readership and big influence, so you should not waste too much time answering that kind of magazines. Yet, the time spent there is probably spent more efficiently than teaching Wikipedia to 20 people at a time, so such requests should be treated at a somewhat higher priority.
Political lobbying requires lots of work, but has potentially enormous impact. We are talking here of changing the law for decades to come, a law that has importance across the board in the whole music and film publishing world and a law that would determine the practical possibility of obtaining certain contents under a free license or in the public domain. There are also further repercussions: it is quite certain that once they get that extension, the copyright lobbies will start working on some further extensions of rights (read here: restrictions of other people's rights).
Another reason why this issue should get high priority is the schedule. For many of our activities, it does not matter much if we do it this year or next year. Wikimedia France is currently financing the digitization of old documents, but it would not be that much of a problem if that were postponed by six months. The problem with laws is that once they are voted, they are very difficult to undo.
How to act
Do your homework
The first step is to look for other groups working in the same direction as you, especially groups with some lobbying experience. In France, for instance, there is a free software group called APRIL that has experience with political lobbying. We exchange informations with them.
The second step is to gather all relevant documentation, laws and regulation. You must know them very well.
The third step is to understand who is pushing for what. There are lots of groups with diverging interests with respect to copyright law, even groups you never suspected existed. You must understand what the various stakeholders are pushing for.
This is sometimes not so easy as it seems, because some groups may have conflicting interests. For instance, during the discussion of the DADVSI law, if I understand correctly, the Press was lobbying so that they could get a kind of larger "fair use" exception for their benefit (e.g. reproducing pictures of works of art without paying the artist, and so on), while not giving other people the same benefit for reprinting press content.
This may sound self-evident, but groups fight for what will bring them money and against what will cost them money (directly or indirectly, e.g. through increased workload or liability). Understanding where the money goes therefore helps you understand who pushes for what.
Talking to the public
Then, there is action. You'll face a uphill battle trying to inform the public. Copyright law is not considered a mainstream topic. Furthermore, most people have wrong ideas about what copyright law allows and what it doesn't allow. In many cases they confuse something being legal, and something being illegal but not prosecuted in most cases in practice. They also often mix up "being legal" and "being ethical".
In short, do not assume that the public knows anything about law. In France, some major politicians make suggestions that are clearly unconstitutional in order to score political points...
There is a pitfall there, into which fall many people from the free software or free content community trying to speak to the general public: too much jargon, too many acronyms, too much text. You need to talk in terms that your public understands, and keep it short and to the point.
(For instance, normal people do not talk of "licenses" - "license" is a terminology of the software industry and the free software community, not of the music or film industries, and certainly not of the general public.)
The legal phrases may be slightly confusing there. In some countries, such as France, copyright is split between authors' rights (which apply for writers, composers...) and performers' and producers' rights, known as droits voisins (literally, "neighbouring rights", because these rights are very similar to authors' rights). Needless to say, the general public has only heard about the former, and almost nobody knows what neighbouring rights are outside of the intellectual property folks.
When a group writes leaflets etc., there is a "design by committee" effect - everybody wants to have his point, his part of a sentence, and the final result is bloated. Don't hesitate to cut. As we say in the education world, one idea at a time. If you need to convey several ideas, do them in separate stages.
Use concrete cases where the proposed law may affect people. Tell them that they will not be able to find legal free orchestral classical music that music teachers could burn on CDs and hand out to students. Tell them that Wikipedia was expecting to be able to put up such kind of music directly linked from pages about composers, but will be prevented from doing so.
Tell them that the music and film industry lobbies are looking at them as cash cows and this ought to stop. Indignation works well.
Do not try to explain fine points of law. Use simple images and simple terminology. You may have to simplify certain issues and represent only the most common cases — the nitpickers in the geek community may disagree, but the impact on the general public will be greater.
Do not appear to be nitpicking on technicalities. People dislike lawyers as folks who have criminals walk free on legal technicalities. If you appear to be defending something that is technically legal but that is considered unethical (for good or bad reasons) by the common folks, you may win in court but lose in the court of public opinion.
Talking to the press
Journalists report daily on many topics. The consequences are that they have short-term concerns (they often want answers immediately, because their paper is for tomorrow), and that they often report on issues that they do not know much about. In addition, as said before, copyright law is not really a mainstream issue.
As a consequence, you should really make it easy for journalists to report on your action. Prepare press releases. These short be ready for cutting'n'pasting into the journalist's paper, so they should target the journalist's audience. If necessary, prepare several releases catering to different publics.
Your press release should contain quotations from named individuals. These quotations make the text more lively, less impersonal. Furthermore, journalists like them because they give the impression to the reader that the journalists went out of his way to interview people. There is no need that the individual in question uttered the sentence you cite - just write the press release including quotations, then get approval from the person you quoted.
My experience is that journalists do not read FAQs or other documentation. (They read what other journalists write, and copy their "facts" from there.) You definitely need a FAQ, but you should not think it is enough.
Protests and photo ops
Do not attempt street protests unless you're absolutely sure you're going to get really many people. If you stage a protest but you are few and between, your opponents will say it proves you represent nobody in society. Rather, stage small events that can show well in media reports even though few people were involved.
Example : you lay a wreath in memoriam to the public domain in front of the government agency that implements copyright, or some other important government building. You need few people and that makes a nice photo op.
Talking to politicians
With respect to politicians, the problem is different. On the one hand, politicians feel the pressure of lobbies - they know that powerful lobbies can create trouble for them — another reason why you should have investigated who lobbies for what beforehand. On the other hand, they wish to do something that makes them visible, some positive points that the public can associate with them.
The lobbies can play dirty. During DADVSI, a music rights management group allegedly threatened cutting funding for spectacles in the constituency of a member of parliament who refused to bow to their interests. The major music labels also enrolled big popular stars to talk against certain proposals and the politicians who made them.
You have to "sell" your point to the politicians. They must have a reason to support your cause, something that they can later "sell" to their constituents or fellow party members.
Arguments in favor of the change, and how to counteract them
There are artists who made music, in particular rock music, in the 50's and 60's, but are now old. Their performers' rights are often their sole pension. If these rights lapse after 50 years, they will not get any more money for their old days.
Producers need money to finance young artists. The money collected on old records is thus reinvested.