I know what you're saying. Students can generally understand the grammar point, but have difficulty putting it into practice. I recommend taking note of common errors that you hear during the production stage. Then, review the errors at the end of class and also at the beginning of the next class.
There are some speaking activities that practice using present unreal conditionals, including conversation cards for giving advice, a role play, and a game board at http://www.eflsensei.com/?scategory=33
All the best!