It depends on whether it is a common species or a rare species, and whether or not it can be identified via pictures alone.
Many common species of visually-oriented animals, like birds and butterflies, can be identified via pictures alone. Take a look at a lot of pictures, but also look for online field guides or identification guides which might tell you which species are commonly confused with that species and what the identifying characteristics are.
For some other species that aren’t as visual, including many reptiles, amphibians, and invertebrates, you might need more specific information to ID them, including their known ranges or scale characteristics. Some of that information can be found on online field guides - check particularly to see if someone has created such a guide for your particular state. But not all of the information is necessarily there - especially for rare or recently described species, the best thing to do is to find the paper that defined the species and/or any papers giving identification keys which include that species. For reptiles it’s easiest to check the species page at http://www.reptile-database.org/ for relevant papers, for amphibians check http://research.amnh.org, you can also search researchgate.net, academia.edu, and Google Scholar.
Of course, the other thing you can always do is ask. Who is an expert on the species you are interested in? Ask them how they identify it.