Ojalá que...

Ojalá que is always followed by the Subjunctive, in either the Present or Past forms.
Present Subjunctive is used when what you are wishing is still (even remotely) possible: The Imperfect (Past) Subjunctive is used when expressing a wish for something that is not possible.  For example, Wishing to redo the past or transform yourself into another creature.
Ojalá que Mauricio venga a clase temprano. Ojalá que Mauricio viniera a clase temprano.
I sure hope that Mauricio comes to class early. [unlikely, but he still may] I really wish that Mauricio had come to class early [but he didn't]
Ojalá que gane la lotería. Ojalá que ganara la lotería.
I sure pray I win the lottery [unlikely, but who knows?] I really wish I had won the lottery [but, alas, I did not]