This script will take what ever you have selected, group and add a '_Group' suffix. Very simple, but I use it often.
import pymel.core as pm
import maya.OpenMaya as om
# List our selection
sel = pm.ls(sl=1)
# Check to see if you have objects selected or not.
if len(sel) < 1:
# No objects selected? Display this message.
om.MGlobal.displayError("No objects selected.")
else:
# 1 or more objects selected? Group all of them and
# add '_Group' suffix
for item in sel:
pm.group(item, n=str(item) + "_Group")
It took me a while to get that Syntax Highlighter script working, but it was worth it. Click the little question mark in the top right of the code to find out more. Fantastic!