In my first year of a research postdoc in math, I think I may want a teaching-only career. How should I prepare for the job search? I got my Ph.D. in math in the last year and am currently in the first year of a 3-year research-oriented postdoc at a large public American university. I am finding it harder and harder to focus on research, not necessarily because of teaching, but for various reasons which I don't think are relevant to the question, and I am beginning to think that I would like a career as a lecturer. I enjoy teaching quite a bit, and I think I'm fairly good at it. If, as I originally intended when I accepted the postdoc, I still planned to apply to research-oriented tenure-track positions, I know what I need to do to be prepared for that process (whether at a large research school or a smaller college which still requires research of its faculty, e.g. a tenure-track position with somewhat higher teaching emphasis). But it seems from looking at purely teaching postings on MathJobs that, for example, I will definitely need three letters of recommendation addressing my teaching. I honestly don't know how to go about finding people to write these letters (for the tenure-track career path I would expect to have to get one teaching-oriented letter). I have a teaching mentor who has observed me a couple terms who could presumably write one letter, but I don't know about the other two. Do chairs write teaching letters? I'm frankly a bit afraid to tell anyone at my institution that I'm not sure I want to do research anymore, since they hired me with a reduced teaching load to give me more time for research. I actually really like the place where I am, and think, at this point anyway, that I would like a lecturer position here, but as I'm currently doing a postdoc here, I have no idea how likely it would be to be hired as a lecturer (even with, let's say, an excellent teaching record). 

Note that I'm talking about a lecturing position, where the only expectation would be teaching and possibly also service. I'm not talking about the tenure-track jobs with more teaching emphasis which still require some research output (although I guess it's possible, though by no means certain, that the research incidentally produced from my thesis could make me eligible to be hired for such a position). But I think that I really just want to focus on teaching (preferably at the university level).
Not as a complete answer, but as information the questioner and others might find useful:

At an R1 U.S. university, for example, it would be difficult for a postdoc to make a transition to a longer-term lecturer or even adjunct... if only because those positions are spoken-for, and quite competitive in a certain localized sense, which happens (in my observation here in Minneapolis) to not be entirely bad, insofar as there is tacit (which is bad) recognition (which is good) of seniority and experience and such things.

A few faculty may be "outraged" that you "betray" the "research Grail" by deciding as you have, but you have to write that off. Most faculty will be very understanding that you've "achieved clarity", for whatever reason. They will also understand that you need to be able to document teaching and pedagogy and mentoring. NB, it's not just "teaching", but a larger thing, "pedagogy", and a somewhat-different thing, "mentoring". Senior-projects, participation in REUs, and similar, are relevant.

And, somewhat nonsensically, an unfortunate fraction of the up-scale four-year colleges have created the concept that "undergrads do research", so you should be careful to not over-promote any potential disaffection with (actual?) research in your job apps. That is, the spin in those cases would have to be that you've had some epiphany about preaching to the masses about . You'll not want to play that stunt for serious undergrad teaching places, though, because they'll probably think you don't understand (the) reality. :)

So, yes, actively discuss with your faculty there, and actively arrange to have people (faculty) have some acquaintance with the broader range of your activities. NB, "not just teaching", but pedagogy, mentoring, ... maybe outreach... The sane people will be understanding, if maybe not very interested personally, and some should be interested enough to help you document your efforts (presuming you make them!) in the directions you want to claim you care about.