1) Determine where are the hydrophobic or hydrophilic residues concentrated? Where does your mutation fall relative to these clusters and to the inside/outside of the protein?
2)What (if any) are the primary partner(s) or binding site component(s) [such as a heme, DNA, GSH (Glutathione)? It should be obvious to you if you have one of these, because it is distinct from the protein-it will be colored differently in the ribbon view AND look like DNA, or be very small and/or not constructed like a protein (recall heme was a wide, flat object) . Is your amino acid conspicuously close to or interacting with any of these components?