first of all, do a visual check to see if the rubber boot has broken. If it is, replace it. If you can't see the condition, just push the front of the car down and listen to the squeak. Once you confirm your push will reproduce the squeak, spray the ball joint very heavily with silicone lubricant. Then do the push again. If the squeak goes away, you got your answer.

If it does not, go to the next suspect, spray and push etc. You will find the worn part very quickly.