1. Sentence Structure Basics: Subject and Predicate
Subject. The subject is what the sentence is about.
For example: John gripped the edge of the cliff with only his toes. Is John crazy?
Predicate. The predicate is what the subject is up to. In other words, the predicate “completes an idea about the subject,”
For example: John crawled up and over the cliff, and he laughed uproariously. A subject almost always includes a noun (there are some exceptions), but a predicate must include a verb.
Sometimes, a subject isn’t included in the sentence but just implied.
For example, Don’t hang off cliffs! 
Here, there is no subject, but it’s implied by the context.

2. John and the cliff

3. The 4 Types of Sentences
When you put a subject and a predicate together, you get a clause! (Yes, like Santa.) The fun thing is you can combine clauses together to form different types of sentences.
Good writers vary the types of sentences they use. For example, don’t use too many simple sentences. You might sound childish. However, if you use too many compound-complex sentences, your writing might be too difficult to understand

4. Simple Sentences
Simple sentences contain a single clause (i.e. one subject, one predicate). Here are a few examples:
John fell off the cliff.
John shouted in pain.
John was silly.

5. Compound Sentences
Compound sentences contain two independent clauses (independent because they could be their own sentences) which are joined together with a coordinating conjunction (i.e. and, but, or, so) AKA Fanboys Here are a few examples:
I didn’t know why John clung to the cliff, but Mark did.
I asked him why, but he wouldn’t tell me.
I stopped asking, but I still wondered.

6. Complex Sentences
Complex sentences contain one independent clause and one or more dependent clauses (dependent because they couldn’t be their own sentence) which are joined together by a subordinating conjunction (e.g. that, because, if, etc.)
Everything changed when clung to the cliff.
Whenever I look at the cliff, I would think about hanging from it, too.
Even though I would never do it, I thought about it all the time.

7. *Here’s a full list of subordinating conjunctions.
Subordinate Conjunctions
after although as because before even if even though if in order that
once provided that rather than since so that than that though unless
until when whenever where whereas wherever whether while why

8. Compound-Complex Sentences
Compound-complex sentences contain at least two independent clauses and one dependent clauses. Here’s a long compound-complex example:
Sometimes, when I looked at the cliff, I would go closer to look over the edge, but I would quickly stop myself because even I didn’t want to die.

9. The true cliff

10. When Sentence Structure Goes Wrong 1. Comma Splices
What if you decided to take two sentences and join them with a comma instead of a period? (Or, for the grammarphiles, what if you joined two independent clauses with a comma but left out the subordinating conjunction?)
Well, you would have a comma splice, and comma splices are bad.
Here’s an example of a comma splice:
John broke his toe, he shouted in pain.
See what I mean? Don’t do that.
Instead, just put in a conjunction (and, but, or, so) or replace the comma with a period.
John broke his toe, and he shouted in pain. OR
John broke his toe. He shouted in pain
Isn’t that better?

11. 2. Fragments
A fragment is an incomplete sentence. It might have a subject. It might have a predicate. It never has both.
Here are a few examples:
John broke his toe. And shouted in pain. (no subject)
Everything changed. When John drove off the bridge.
Fragments are against the rules, but in certain situations, they can be used effectively as a stylistic choice. However, unless you know what you’re doing, it’s a good idea to avoid them.

12. 3. Run-on sentences
A run-on sentence is kind of like a comma splice except you take out the comma. Here’s what I mean:
John broke his toe he shouted in pain.
Run-on sentences are bad. Put a period in between those clauses!

13. PRACTICE
Write a story about a guy who drove off a bridge. In your story, use at least one example of each of the four types of sentences we talked about above. Avoid the sentence-structure pitfalls.
Write for fifteen minutes. When you finish, post your practice in the comments section. And if you post, be sure to leave feedback for your fellow writers.
Have fun!