"How to" is an English idiom for an instruction guide that tells how to do something. Threads that start with "how to" serve the same purpose. Threads that ask questions should start with "How can I" so that they will not cause this confusion by inappropriately using the "how to" idiom. There has been an alarming incidence of recent threads starting with "how to" that are not guides.
http://en.wikipedia.org/wiki/How-to