The cracked corn and the sunflower seeds do work well but I found something that even works better. I started putting these out to attract the starlings, which showed up in large numbers, but I quickly noticed that the squirrels went nuts for em (no pun intended).
What are they???? The solid suet cakes found in the bird seed sections of most stores,,, but make sure you get the one that list nuts in the ingredients. I buy them from "Home Depot" for .99 cents each and the label says "Nutty Treats Suet Cakes". They have roasted peanuts, millet and corn mixed in with the suet and I'm tellin ya they attract squirrels like magic.
Give em a try, you won't be disappointed. As a side benefit you should see quite a lot of starlings show up also to give you some added targets.
Jeff