What are some ways to discipline a 15 month old?

My son just started acting up and not listening to us and we are very stressed and frustrated.We have tired time outs and he still doesn't listen and throw tantrums..Basically he does what he wants.We ignore the tantrums and whining and don't give in to him or anything, but what are some ways to make him learn he has to listen?any advice would be helpful. This is our first baby :)