What is the difference between the past particles "guo (过)" and "le (了)"?

Guo (过) refers to something a person has experienced in the past, versus le (了), which refers to someone just having done something in the moment. For example, someone who is telling you that they have visited India several times would use the particle "guo," whereas someone who is telling you that they already ate lunch would use the particle "le."

What is the megablunder error in the following sentence and how do you fix it? "Bob decided that running home in the heat was better than to wait for his mom to pick him up much later."

The error is Parallelism, and one aspect of this rule is that verb forms have to agree with each other. In the above sentence, "running" and "to wait" are not parallel. The correct sentence would be: "Bob decided that RUNNING home in the heat was better than WAITING for his mom to pick him up much later" or "Bob decided that TO RUN home in the heat was better than TO WAIT for his mom to pick him up much later."

What is considered a well written essay?

Contrary to what most schools teach, essays do not have to be restricted to the basic five body paragraph essay in order to be considered a well written essay. The essence of writing a very good essay is determined in your thoughtfulness and structure. It is important to stay on point and not stray from the question asked and also important to not ramble. An essay does not have to be long, either, to be considered a valid written piece. As long as you say what you have to and keep it concise and well thought out. Although an essay does not have to be five paragraphs, it's essential to ensure that your essay form and structure is done well. That is to say, your introduction should introduce the topics discussed in the body paragraphs, each paragraph sticks to one topic, and you transition well from one paragraph to the next.