Tim,
Ed's got a point on the standard 'T' instrument layout. I believe Cessna changed the layout around 67-68, to the standard 'T' layout, by moving the radio stack over to the right an inch or three, thereby allowing more room on the left side of the panel for instruments.
Not meaning to tell you how to buy a plane, I'll enlighten you on my choices. This may get drawn out a bit, but bear with me. First, study the year model(s) and choose
which model will suit your needs. I'm
rather tall,

so that ruled out the earlier models with the smaller, angled door. Secondly, mainly for asthetics, I chose the newer cowling on the 71-77 models, as they have the 'controversial' nosebowl mounted landing light, the 6" prop extension and the newer looking cowling surrounding the prop plus, a flatter instrument panel top contour vs. the older rounded top.
I'll list a few items I had on my list but, keep in mind, and I don't mean to step on any toes here because everyone likes their 'very own' planes, but these met the criteria for what I was looking for:
(A)
NO pull handle for the starter.

I wanted a key start. Nothing against the guys and gals with the pull handle, but again, just personal preference.

(B) Extended vertical fin on the empenage. Again, a '71-'77 model feature.

(C) Standard 'T' instrument configuration.

(D) Circuit breakers

(E) Low(er) time airframe, and again, without opening a whole 'nuther can-o-worms,

this number varies per individual. Mine was set for a maximum of 5000 hrs. TT, although, I just about went a touch higher on one plane.
(F) Engine time in the area of 200-300 SMOH or STOH. (Boy, did I ever blow it on this choice!)
(G)
NO damage history. Light hanger rash is acceptable.
(H) Paint: not really and issue, as I'd plan on getting to that later in a scheme I like, but a 'plus' if it's already painted.
DO NOT get excited about pretty paint and that's all I'll say about that.

(I) Interior: Clean but not a lot of broken plastic or worn out seats. Usually, this will give you a good indication of how the owner felt about his/her plane.

(J) Avionics: Minimum, (1) Digital flip-flop nav/com, VOR head, mode-C transponder, encoding altimeter and an intercom, portable or panel mount. Panel mount is a plus.

(K) Pe-buy inspection by a third party,
your mechanic
and a buying buddy to look it over with you. The 'buying buddy' is the best thing going, as I had several club members, so graciously, take a look at a few of them for me. This. in itself, will save you a bunch-o-cash on airline tickets and I am forever indebted to those who looked for me. And, if you can't look at it yourself
GET PICTURES, lots of
DETAILED PICTURES from a fellow pilot who knows
WHAT to look for on a 150!! I can't stress this enough.
(L) If the owner doesn't answer questions to your liking, rephrase them. If you
still don't get the answers you're looking for, thank the seller for his time and move on. The answer I ran across the most was: "It was like that when I bought it.", without any further explanation. Get that answer about 3 times on one plane and it's time to go home.
(M) All logs present and accounted for. Spend an hour or so and go over them if you like the plane. It's sorta like looking at someone's medical records and you'll come away a bit more educated.
(N) If it's getting serious, order the FAA CD title search/lien/owner history. You may learn a lot
before you buy. In one particular instance, I did! Best $100.00 I ever spent!
PRICE: Settle for a range you wish to work with. Mine was 18k-28k, and I may have gone to 32k, but it all depends on what
you're looking for and what you're willing to spend. When it's all said and done,
you're the one that must be happy.
As for everything else, perhaps others will chime in with their specifics.....YA THINK? Naw, not around here! Good luck on your search and keep us posted.
Bengie
P.S.
I finally ended up with a '76 M-model, 1694 TT, AF&E, NDH,(with a little hanger rash), circuit breakers, wheelpants, original paint, original interior without tears or any major broken plastic and within my price range....and.... I'm happy.
