I am in the process of purchasing a 3-D Printer I am fairly new to this field and would appreciate any tips on creating 3-D printable models using Sketchup.
Maybe one of the most common tips is to plan to model at a larger scale. When I model for 3D printing I set Units to meters and treat mm or inches as meters. This makes it easier to create manifold models which you need to be able to successfully print. If the slicer software you are using allows you to define the import units for the .stl file, you don’t need to scale the model down before exporting. By design, .stl files are unitless so you can export at meters and import in mm or inches as appropriate.
There are some extensions that can be useful such as Solid Inspector2 and CleanUp3 from the Extension Warehouse and TIG’s Solid Solver from Sketchucation.