I agree with @PeterJansson that impact factor is certainly an important factor in selecting a journal. But I would also think about who you want to reach with your paper. Although Google Scholar and similar search engines now ensure a much higher probability of finding your paper based on its title, abstract and keywords, it will only be found by people actively searching for terms associated with your work.
Most researchers still subscribe to specific journals in their field, even if only through e-mail alerts, so I target a journal also for its audience (while trying to select the highest impact factor from this subset). This is especially important if your work bridges several fields.
For example, my research is about human-robot interaction, so I have to decide whether to publish an article in a journal that is read primarily by roboticists or social scientists/psychologists.
In this case, it is also vitally important to adjust the paper to its target demographic. Psychologists don't know (and likely don't care) about my implementation details while roboticists are more likely to be interested in nitty gritty details about the code and less about the nuances of the social psychology theory behind it.