How do I use the imperfect subjunctive?

The imperfect subjunctive has a variety of uses:1) You can use the imperfect subjunctive when the independent clause in a sentence (main clause) refers to the past. 'Quise que me ayudaras a entender el subjuntivo' I wanted you to help me understand the subjunctive.  2) You can also use the IS when the independent clause refers to your current emotions/doubts about something which has happened in the past. ' No me parece que la boda fuera tan grande.' It doesn't seem to me that the wedding was so big. 3) You can also use the IS to indicicate when you hope for something but it is unlikely to happen. (always Ojalá) Ojalá pudiera estar contigo hoy. If only I could be with you today.  4) The IS is used in 'If' clauses, when the statement is something which is unlikely to happen. 'Si yo ganara la lotería, viajaría por todo el mundo' If i won the lottery, I would travel all around the world.  5) Using only the verbs deber, querer, or poder, you can use the imperfect subjunctive to make a very polite suggestion or formal request. ¿Pudiera ayudarnos?Could you please help us?