I'm thinking about mystery writing. An appealing aspects about writing a mystery novel is thinking like a criminal and then finding flaws in the various methods (clues). One of the first things you probably should do is decide as to what the mystery is about, theft, murder, kidnapping, etc. A downside to writing mystery is that structure is very important, while it maybe possible to write a mystery freestyle, I would never try. The ending, who committed the crime, how, and why are some of the very first things you should probably figure out and then write around that.
Say you decide murder, then you have to decide is it premeditated or spontaneous? Does the criminal have time to create a cover story? Do they try to dispose of the body, create an alibi, make it look like a suicide, etc. What kind of skills does the murderer have? Do they know forensics techniques and plan accordingly? Do they know how and have the time to create false leads such as faking DNA?
I was thinking about how a criminal would dispose of a body and the problems (read possible giveaways) for each method I could think about. There are a number of ways to dispose of a body. Here are some and some problems with each method (there are of course problems with the methods I did not bring up, ways around the problems, and other methods of disposing bodies).
1. Bury it. The body must be buried deeply because shallow graves are far more likely to be found. Some of the problems with burying a body: takes far to long to dig a deep enough hole and topographical conditions may prevent you ex. mountains where soil is thin and full of rocks or a swamp/wetland where because of water level you can't dig deep because the hole will constantly fill with water. Burying the body in cement under a sidewalk would also not work very well because the stench would steep through the sidewalk as the body decays.
2. Throw the body in the river. While this maybe an appealing method to dispose of a body it has a lot of downsides. The most obvious being bodies float and would be likely to come ashore fairly quickly and be found. Taking that into account the criminal may try something like putting concrete shoes on the person which also would not work since the body will fill with gases and become bloated from the natural process of decay which will make it more buoyant and float. To keep the body under water it would require an amount of weight that is greater than the weight of the person. Lets say that the criminal took that into account as well and decided to chain the body to a large rock at the bottom of the body of water, this would not work as well because as fish eat at the body and the body decays naturally it would eventually break up and pieces would make there way to shore.
3. Burn it. It requires a large amount of flammable material to burn a body, taking several days to burn most of it and bones would still be left. Compounding that problem is that the body would smell as it cooks. Doing something like pouring gasoline on the body would not be a good method since it would burn the outside of the body but the inside would not be burnt.
4. Use chemicals or acids to break the body down. The bodies would stink a lot as it breaks down and it would leave a tub full of human slime.
5. Have animals or trick people into eating the body. The largest downside with this, purely from a disposing of a body point of view, is it is very time consuming. It would take a lot of time to prepare the body and there would still be traces in the excrement.