I used to stick a toothpick in to test doneness.
I have come to see the tops and know... I open the oven touch the top of one to confirm and spring back to the touch. For me, it's generally 18 minutes at 350 degrees.
Cakes are tougher since each size is different and they get filled at different levels at times but touch tests work and I confirm with a stick in the bigger cakes (half sheets).