Try just searching Google. That usually helps... :D

Duolingo does not explicitly teach grammar, you have to pick it up from the examples given. It can be very tough sometimes. When I was doing German, there were some tricky points that were just passed over that didn't seem right to me.

When you open a lesson such as "Basics 1", you will see several spiral notebooks that contain each of the sub lessons. Beneath the spiral notebooks is a section labelled, "tips." This often includes information on grammar. Also, you will find grammar information under the section next to "tips" called "discussion". In addition, if you mouse over words during a lesson, you may find some grammar tips such as conjugations.

But, as rocketthebunny mentions, many use outside grammar sources alongside Duolingo.

As for practicing grammar, that is essentially exactly what Duolingo has you doing all of the time.

Thanks, I'll have to have a look on google. I've done AS German so I have learnt and understood the basic rules once, but having not done it for a year I've kind of forgotten them and I need a refresh :) I hoped there would be some sort of exercise specifically for learning the grammar rules thoroughly, but Duolingo is a great site regardless :)

On a similar note, is there any way of practising the gender of nouns that you've learnt?