I use a screw driver. Release the 4 tabs across the top of the grille first. Wedge the screw driver in between the grille and core support, and pry the clips loose. Then under the bottom corners, try to get your fingers underneath, and give a good tug. With a little bit of wiggle room, you should be able to slip your fingers behind the sides of the crossbar of the headlights enough to pop the inner clips out first, then the outer ones.
If you've never taken your grille off before, then the clips will be tough, even though I've removed my grille/crossbar more times than I can count, it still takes some effort, although it's easier now, than the first few times I did it.