Copy and paste in X

Since most of my GUI life has been in the Windows world,
I am having a really hard time doing copy and paste under
Linux.

In the Microsoft and Mac worlds, copy and paste are
very straightforward and consistent. But under X,
I run into several different treatments.

The classic X treatment is that a string is copied if
you highlight it. But then if I go to a browser's
address line, and highlight its contents in order to
replace them, I have just wiped out the clipboard.
So instead I have to click at the end of the previous
URL, and backspace to kill it before center-clicking
to paste in the new one. What am I missing?

Different apps seem unwilling to paste each other's
stuff. Some have what looks like Windows-style
copy and paste, but the results aren't available to
other applications.

Is there an option in X to permit Ctrl-C to control
the copy process, and Ctrl-V to paste? And some way
to ensure use of a common clipboard for all apps?

Vic