Tricks for knowing when a cheesecake is correctly done I have just made a cheesecake, (not my first), but will admit that for me it is a bit of a guessing game to know when it is perfectly done.    I know that the sign is when the middle still jiggles, but how big of a middle?  Dime size, nickel size,  quarter size, or salad plate size?  Fortunately, luck was on my side and it turned out perfect, but not without worrying about its doneness!  Other than the "jiggle", is there any concrete way of knowing when it is done?  Is it possible to use a thermometer for the middle and what would the temperature be?  Luckily, even if a cheesecake is under or over done, it's still delicious, but when serving it to company, it an added bonus if it turns out perfect!  Any tips?
I use a therometer. 

King Arthur flour suggests measuring 1 inch away from the edge of the cheesecake and looking for a temperature between 165F and 170F. 

Americas Test Kitchen/Cooks Illustrated has recommended 165F in the center (checked in 20 minute intervals, provided that you're not close to 165F). However, I remember on the television show that they said 150F many years ago (their blog uses 150F in the center for some recipes too; others say 150F but don't say where to measure it). 

I find that the King Arthur method comes out a little bit overdone, so I generally err a bit lower to 160F for 1 inch away from the edge of the cheesecake. 

This is all assuming a 9 inch springform (certainly, this will make a difference for the edge based methods, not sure for the center based methods if you change the size of the pan); Your desired temperature will vary based on recipe, but I've tried this with a few recipes and had good results. I generally use recipes which have just cream cheese, eggs and sugar (and maybe a bit of flour) along with add-ins (pumpkin puree+spices for pumpkin cheesecake or lemon zest + berries for a berry cheesecake) for the filling (no sour cream or ricotta or other stuff). Some of the recipes I've tried don't use water baths, others do. 

As for aesthetics, I always poke in the same place, and make sure when slicing that I cut through the hole. People don't notice -- they're too busy stuffing their face with cheesecake.