Germaneness (spelled it wrong originally) is actually pretty easy to establish. It has to be in the same "section" of law in order for it to be germane. In Louisiana, Title 22 deals with insurance. If you want to amend something in Title 22, the law can ONLY amend things within that Title. Even if, in order for that new law to work you have to amend something somewhere else, you have to have a 2nd bill to make that other change.
For instance, if you wanted to create a new health insurance website, you'd need 2 bills. One to change something within Title 22, and another to change Title 47, which is Revenue and Taxation, on order to fund it.
Not the MOST efficient use of time/resources, but the tradeoff is a bill that is VERY easy to understand and which cannot be hijacked to carry something else.
Also, you can go even one step further. Here in LA and in other states, they have enhanced rules that say that you cannot even step across certain Sections within a Title. For instance, you cannot stick a homeowners insurance change onto an auto insurance bill (being that they are numerically different Sections of the same Title).