How do I remember which nouns are neuter and which one aren't?
In general, you should memorize the gender of each noun with the word. But, you can also remember that there are certain endings that will almost always correspond to one of the three word genders. Words that end in -chen, -lein, or -li are extremely likely to be neuter.
How long should I make my paragraphs?
In general, a paragraph shouldn't be longer than a page, but should be more than a few sentences. Each paragraph of your essay should be making one larger point that relates back to the main thesis of your essay. So, you need at least one topic sentence that tells you what the paragraph is proving, and a few more sentences to prove it?
How broad should I make my thesis statement?
Think of your thesis as being like the hypothesis that a scientists sets out to test with their experiment. Your thesis should be a specific statement that can be proven right or wrong, not a vague statement. "There's a lot of plant imagery in A Midsummer Night's Dream" isn't very good, because it's not specific enough. How much is "a lot"?