Clap, whistle, call them... And if you have your doubts, always call a vet.
I've known deaf pets. They're more in tune with their other senses, so things like tapping your foot on the ground to get their attention and teaching them what you want with sign language (or a form you're more comfortable with) works really well. Dogs are pack animals. They're used to reading body language so it's no surprise that sign language is good for them.
I'm no expert on deaf pets, but my mom volunteered in a foster group since I was 7, so I picked up a little bit.