Valuing a company not only involves working with numbers and predicting future growth but looking at a more general and subjective view of the company.
This all starts with the managers who are ultimately at the top making the strategic decisions. To asses the strengths of the management you need to find out things like who runs the company, where do they come from, what experience do they have in their various capacities. Are you dealing with a 20 year CEO or a 20 year old with out any prior business knowledge. Just because a company has bad management doesn't mean it's doomed but it's a definite red flag to investors.
Another thing to consider is why they are actually in business. What does the company do to make money? Knowing what a company actually does is fundamental to making a sound investment. It is surprising how many people own stock but knows nothing about the company.
Analyze the competition. Find out who the other players in the industry are and see where they stand in comparison. You don't need to make it too complicated but try to get a feel for the company and its competitors. With this information you can also get some ideas about what to expect for growth in the future.
Look at the advertising the company puts out. This is usually readily available information and an easy way to get a feel for what message they are trying to convey to the public. Many times you can order their prospectus which can contain a treasure trove of information such as general financials, brochures about the company and so on.
If you take a step back, take a deep breath and approach valuing a company with a general, rounded view you might get a completely different sense about the company than you initially had.
Sometimes, such as with penny stocks, there is not much information available to the public. Those companies are usually new startups and don't publish adequate information to determine much, if anything, about what makes it tick. In this case you might consider a stock picker newsletter, such as