If you install N52 properly, it comes with a software. Then edit the profile you have for wow and change one of the keybindings as a MACRO --> NEW MACRO.

Start Recording (ignore delay on keystrokes). press the 2 buttons you'll be reserving for Renew on your warlock and Renew on your pet (mine is just simple 1 & 2). In my macro it's press #1 then delay 7 seconds, then press #2, then delay 7 seconds. On the right, under the last options, click the box that says REPEAT UNLESS PRESSED AGAIN. This will continuously keep casting renew onyour warlock and your pet.

Leaving your warlock nearly invincible against 1-4 mobs without having to pay attention with the healing since Renew in non instanced / non elite mobs are more than sufficient. Improved Life Tap FTW.