The form for the Subjunctive and Ojalá is the required 3-part formula.
Present Subjunctive is used when what you are wishing is still (however remotely) possible:
|Ojalá que Mauricio venga a clase temprano.||I sure hope that (God willing) Mauricio comes to class early. [unlikely, but he still may]|
|Ojalá que gane la lotería.||I sure pray (May God will that) I win the lottery [unlikely, but who knows?]|
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 viniera a clase temprano.||I really wished that (if only God willed that) Mauricio came to class early [but he didn't]|
|Ojalá que ganara la lotería.||I really wish (if only God willed that) I had won the lottery [but, alas, I did not]|