As someone who has been a noob for a long time, I found there are some plugins for cleaning up the model that are helpful at the beginning:
Default layer geometry (get all your edges and faces back on the default layer)
Remove Lonely Vertices (join edges that have unnecessary vertices into one)
FrontFace tool (get your faces oriented correctly)
Make Faces (get faces to form, especially on imported edges)

Everyone would say work with the basics for awhile , and don't make the mistakes in the first place; but plugins like the above help you get back on track, 'cause things happen. Your approach to the work, as in other realms, is probably more important than what tools you have. Starting out one could quickly make a mess with some of the plugins out there.

There are some in the "must have" plugin index that will get you a step further like Joint Push Pull and Fredoscale. Don't forget Sandbox Tools which comes with your SU and can do a lot with contours and manipulating terrain shapes.

Hi,

Why Sketchup. Because SketchUp is very easy to learn. If one has understood the use of standard tools there are very quick steps to the first success. I had found six years ago a video tutorial which consisted of twelve lessons. In these lessons, the use of standard tools were shown. I tried all the techniques shown in parallel with "Sketchup". Within four weeks I was able to take the first small projects undertaken. Of course, I've made many ​​mistakes. Then I Found the SketchUcation forum, and learned much among others the various plugins to know. The rest was practice and practice again and again.

And that's what makes Sketchup. You can learn the use of the standard tools very quickly and you can have great success with. The whole construction techniques are easier to accomplish in Sketchup, as this is the case in many other programs.

Other 3D programs also have their place, because Sketchup is not the "non plus ultra" in the 3D programs. Sketchup has its limitations e.g. in the design of organic shapes. Before a decision is always the question, for what purpose I want to use a special 3D program.

Charly