hydrogen peroxide
depending on size of the dog, start with a small amount (1/4 cup), wait about 5 minutes, if nothing try another small amount of peroxide.
you can pour it directly in their mouth or use a large syringe (no needle of course)
tilt their head back and pour it towards the back of their mouth
they will not enjoy it, so make sure you get them to swallow it.
how many pills did he get into?
you can also usually call the poison line phone number, most likely they will tell you to call your vet though.
Some medications/things are bad to make them vomit.