Most penny stocks are manipulation scams. But, you can profit if you know what to look for. I probably should write an ebook on this, lol. Anyhow, things to look for are:
Penny stocks that under go name changes with little to no volume previously is an indication that they are about to do something with the shell. A forward split is also a good indicator.
Monitor yahoo finance news for filing docs. when they're filed with the sec, they are submitted electronically (edgar) and distributed immediately to all the major news outlets. You're looking for an "8K" document filing. Every company must file one of these when they are going to do a merger or change the business scope or management team, etc. You're looking for reverse mergers.
Also, you could play the shorts...Whenever you get one of those spammy stock promotion emails, or faxes, you can take the company that's listed and look at some moving averages and watch it go up and short the piss out of it because you have real information by recieving that spam...its A stock promotion...also know as a scam. A pump and dump...whatever you wanna call it. 2 laws govern the stock market: the law of gravity, lol, and the law of infinite resources. The second law is important because it reminds us that there is no such thing as infinite resources. Resources have finite limits. Just ask yahoo (they just laid off 4% of they're staff) because the finite number of search users and choosing other search services over theirs!
Sorry for the rant...Back to business.
The stock promoters usually get paid in free trading stock and cash to create liquidity by introducing buying into the market for the penny stock. So they send a blast to the degenerate gamblers, ahem, penny stock traders, and generate huge buying and then you see a sharp volume increase followed by a sharp decline.
Listen, at the end of the day, as with anything, you must do your homework. But if you do, it can pay off. I personally think that there are easier ways to make a few hundred bucks a day.