Heads up! I've posted a follow up to this tip that details a quicker way to comment in vim by using a simple function. Check it out here.

From the “holy crap why didn’t I find this before” category…

When editing in vim, if you find you need to comment out a block of code, try the following:

1. Jump to the start of the line at the top or bottom of the block
2. Press Ctrl+v to enter Visual Block mode
3. Navigate to the end of the block. You’ll notice only the first column is highlighted (for the most part)
4. Press I to enter Insert mode before the first non-blank character on the line
5. Type whatever the comment syntax is for your language, eg. “//”
6. Press Esc to get back to Normal mode.

You can follow similar steps to uncomment the same block,Ctrl+v to highlight the comment characters followed by x or any deletion command to remove the comment.