those yellowish concealers are usually awful in my opinion.

I've tried many drug store ones and one I REALLY love is Maybelline Instant Age Rewind - it's a liquid and comes in a small tube. It stays on strong, covers well, has light texture, feels good and blends well. I was looking into switching to one that had SPF15 in it, I think Neutrogena makes it. But this Maybelline one is really good! It's about $7 at most drug stores-

And the way you use the Maybelline concealer is put 3 small dots under your eye - the inner corner (near your nose), in the middle under your eye, and one on the outter corner. DAB (not rub) these dots from the inner corner to the outter corner and blend.