I wanted to use something different than "Let's go to the party", so I tried "Let's head to the party", but then, I found other examples with "Let's head for the party." I wonder which one is more correct.
They're both correct, but with slightly different meanings.
"Head to" connotes that you're confident that you'll actually arrive. A college student might say, "Classes are over, let's head to the bar."
"Head for" connotes that you're going in that direction, but you might get waylaid or you're unsure of the route. A tourist in New York might say, "We're lost; let's head for the Empire State Building so we can get our bearings."