dozens of methods to launch files. Many locations / methods from within the registry, startup groups, batch files, schedules.

I suppose it depends some on when / how you want it to run and how you want it to look, does a user need to be logged on or not etc..

There is RUN / SHELL / COM SHELL method too

Just look at some system that has been heavily infected with Spyware and you'll see how tricky some of them are at launching there junk.

Can't say as there is only one specific best method as some of it is user preference.