Does it make sense to get an LLM in preparation for "law school?" Someone I know thinks he wants to go to law school and pursue a career in law. One way for him to "find out" is to pursue a one-year LLM degree after graduating college. He has two reasons for feeling this way.

1) Some of his older friends have started, then "aborted" law school programs. Going for an LLM instead of a J.D. would put only one year at risk instead of three. Of course, if he later decides to pursue a J.D., he would have spent four years in law school. Which leads to the second point:

The LLM would enable him to take some, not all, of a first year law program, such as legal writing, contracts, and property, as well as some electives to discover his areas of interest. Given the rigors of a law school program, that would lighten the burden of going for a J.D.later on.

Would pursuing the LLM at a state school (where he is getting a 3.8 GPA) help or hurt my friend if he later decided to pursue a full blown J.D. law program at a good private law school? His idea is "soften up" a law program, but he fears that with a master's degree, he will be held to a "higher standard" for admission.
No. It does not make sense to do a LLM before a JD.

The length of the program is not the relevant thing to consider. 

The standard course is to do a JD -- which is a first degree in law -- before a doing a LLM to gain specialized knowledge. Usually a JD or equivalent is required for admission into an LLM program. 

I understand the confusion since usually a doctorate (JD) comes after a masters (LLM). Note that, outside the US, the first degree in law is often called a bachelor of laws (LLB), which makes more sense.