Last year a friend told me how useful the free program "Grammarly" was in improving his basic writing skills. I checked it out, and I agree. Like all tools, it has to be used properly. Check it out. You just have to be extra-careful to trust yourself if you know that you're right and the program is wrong. This happens all the time. It's better to have a live human being help with editing, but sometimes this isn't possible.
I also use the spell-checker function in MS-Word. Why not? Why wouldn't you use a tool that works, even if imperfectly?


