Today I saw a trick to comment and uncomment multiple lines of code in C. It uses both // and // to comment as below:

/*
    foo();
    bar();
//*/

To uncomment, just add another / in the first line:

//*
    foo();
    bar();
//*/

So you don’t need to change the other end, which saves a lot of time.

Note. Although // is not ANSI C and is brought in by C++, actually many compilers support this format of comments.