What if I don’t want to select a plot style when I print?

No matter, if you have not selected the plot style or don't want to select a plot style.

But for doing like that, if you want good drawing to print then you should know that if your are using Mono-color (Black) Ink then the default style is Grayscale type and if you are using color printer then it will be in acad.ctb as default.

So, color and line type using in your drawings should be considering in which type you are printing.

So I suggest if you are using one color printing then use Dark colors like (RED, BLUE, BROWN etc) for Important lines and Light colors (Yellow, sky etc) for others lines.

Great Answer by Mr. Ramesh, Thanks for explaining in a good way.

All plots are done using a plot style table. If you don’t choose one, AutoCAD uses a default plot style file named acad.ctb, which gives all colors the same line weight, and prints them using the object colors that you see on the screen.  This is usually not optimal.