The 0 Buffer

Here's a Vim 101 thing that I went without knowing for far too long, so maybe it'll help you as well:

Say you have 3 lines of code ...

T-2000
John Connor's Foster Mom
Random Policeman

And you want to replace the second two lines with the first. You might type yy to yank T-2000, then type shift-v and p on line 2 to replace John Connor's Foster Mom with T-2000:

T-2000
T-2000
Random Policeman

But if you go to line 3 and type shift-v and p again, you'll paste John Connor's Foster Mom, because Vim replaces the default buffer with the previously removed line.

Fortunately, T-2000 is still available in that scenario – it's automatically placed into the 0 buffer. To continue to paste T-2000, just type:

"0 p

to paste from the 0 buffer instead of the default buffer.