Hate to be a party pooper, but it will never work.
There are groups advocating the legalization of this or that substance, whether you agree with it or not most of the crap the government has prohibited isn't harmful to you or others if used responsibly and in moderation. The problem is the general public doesn't give a **** one way or the other, and they probably never will. It's concentrated benefits and diffuse costs. Politicians have little or nothing to lose by making/keeping certain substances illegal, even if every user of those substances took their votes elsewhere. However, the benefits are clear and immediate. They get increased budgets for law enforcement to deal with all the new 'crime' that's created, they get to appear to 'be tough' on this or that, and even if doing so is completely pointless it doesn't matter because the majority of the people in the world don't know any better. They get increased control over the economy to help favored companies manage competition. They increase their power in general, which is always a wonderful thing to a government worker, elected, appointed or hired. What do they lose, the votes of an incredibly small minority of people? So what? It'd be no different if they outlawed a certain breed of dog that no one really gave a **** about. Most people aren't going to care, because even though their freedom has been restricted in a very real way it has no practical effect on them. Their oxe hasn't been gored, they don't care. Unless at some point in time they want that breed of dog and then they cry out at the injustice of it all.
We live in a democracy for all intents and purposes. Imagine a bell curve representing the general population and its intelligence. Now think of how incredibly dumb the average person is, and realize half of them are even dumber than that. Then realize that in a democracy all a politician needs to do to stay employed is essentially keep more than 50% of the population happy, or at least not too pissed. 50% of the population has trouble lacing its shoes. I'd hazard a guess that 50% of the population in this country hasn't read more than a few books all the way through, and those only because they were required reading in school. Way more than 50% of the population gets most if not all of its information from television, and sees nothing wrong with that. The government has default control over information and how it's presented through television and public schools, and even though other information sources are out there they really are marginal.
Even the people in that population who aren't that smart but who would help you often can't. They're likely the ones whose oxes were gored, and they got busted for steroid possesion. A lot of times people who get convicted of a felony drug charge lose the right to vote. A lot of times they have trouble finding employment with that on their record. What are they going to do to change things?
I used to be an optimist and an idealist. I still am to a degree. I vote Libertarian, I hope things change. But to be honest the pattern of history seems to be that governments just increase their power on and on over time until they finally piss enough people off and some sort of revolution, doesn't have to be bloody, occurs. In the United States at least people just aren't pissed off enough to revolt in any way. Most of them have a decent life, easy credit, a TV in every room of the house they bought with a government loan, a car to get around in, some kind of medical coverage, someone to crawl into the sack with at night, a pretty nice life overall. I forget who said it, but when it comes to the government it's too late to work within the system to change things, and it's too early to shoot the bastards.
The only way things will ever change, and I'm talking in a small way like making steroids legal but regulated, is if politicians and beauracrats see it's in their interest to change those laws and that in doing so they won't piss off enough people to make it not worth doing. To do that you have to pull money out of their pockets, threaten their employment, etc. They're not going to give a **** otherwise.
One piece of advice, as far as letter writing campaigns go, keep letters to yes or no. I do or do not support this or that law, that's it. Lengthy letters giving reasons and discussing principles get thrown out. Whenever politicians are receiving letters about this or that piece of legislation they usually make three piles. Those in support of the legislation, those opposed, and one pile for the interesting ones written by people who wear tin foil hats to stop the CIA from listening to their thoughts. Lengthy letters discussing principles or not giving a clear yay or nay in the first sentence end up in this third pile or in the shredder. Then they count the other two piles and find a way to justify a position in support of the one that had the most letters. Simple and to the point.
Beyond that there's really nothing you can do. Taking out ads in the paper doesn't really do much, people don't read them. Billboards in he subways don't do ****. The government might actively supress them in fact, they've done so with ad campaigns from marijuana legalization groups. Usually nothing happens, sometimes enough of a free speech stink is made that a judge decides against the government, but in the end the ads usually disappear anyway because few if any people want them there to begin with. The public just doesn't have the specialized information necessary to make an educated decision in most cases, and most of them wouldn't give a **** even if they did have the info, because it doesn't personally matter to them.
Once more, sorry to be a party pooper, but realize how hard the effort will be, and it will likely be ineffective. Not because you're wrong or because there's a conspiracy. People honestly just don't care. If you can make them care, that might make a difference. Look at the case of marijuana again. The biggest and best thing marijuana legalization has going for it is medical marijuana, and even though none of the activists say it of course that's a backdoor to open up the discussion of legalization. It's not harmless stuff but it's a pretty mild drug, and if the medical case gets made, and it's got enough evidence to possibly get through, it becomes more acceptable, more good information is available about the drug to the general public and eventually a choice gets made, and maybe it gets legalized and maybe not, depending on how the public feels basically. It'd depend on their experience, are most people being responsible or are hardcore stoners being assholes and fucking people's **** up? Same goes for 'roids.
If I recall the FDA recently approved a couple steroids the government has been demonizing for a while for the treatment of wasting associated with AIDS and cancer. There's your in. The prohibition of drugs hinders their development. It's possible some drug company somewhere might develop a steroid that truly is safe. One with minimal side effects but with most if not all of the benefits. But even if they can do research, who's going to develop a drug that, if effective, would be on the black market faster than **** through a goose, cause all kinds of bad publicity, etc? That there is a responsible, safe, and necessary role for steroids in the treatment of various diseases, especially politically correct diseases like AIDS and cancer, and that their prohibition negatively affects the development of newer and safer drugs, is a good way to open the door to legalization.
To be honest, I think that's the only route that's worth trying. It simultaneously helps push good information into the public's mind while at the same time generates sympathy and support in that same public. Good info doesn't matter if they don't give a ****, and even if they do care and admit steroids can help a few people who need help bad, it doesn't matter if they still think steroids in general come from Satan and are evil.
At least that's how I see it, take from it what you will.