Try to make the topology as clean as possible without big peaks sticking out pieces which are not part of the mesh, holes, messy boundaries, etc. The better the mesh is the easier it is for the algorithm to come up with a good unwrap.
Use Clean model before using the Unwrap tool to prevent the topological defects.
If you get a bad result with Maximal texture count style, try using Adaptive texel size style with Minimal required texel size set on Optimal.}
Always use the latest version of RC just in cause the function on Unwrap tool gets an update.