Yes it is good to get variations, but google aslready knows them, if you put SEO, it knows you also mean Search Engine Optimization, so its not like you wont rank for them, you will always rank higher for the variation you use.
but the most imporatant think is, do not go un-natural in order to fit in keywords. Keyword stuffing is a real worrie.
If you cant fit them in without sounding wierd, dont do it. Swaping terms each time you mention the same object can be un-natural. you would not be the first to do it and it would not be the first time SE's have seen it

I'm not sure they dont matter, i would think that .pdf, .doc and. xps for example would be less usefull than a htm, asp, aspx.
but David is correct, you are better of not haveing a file name.

I develop using Microsoft Asp.MVC, there are no file names in MVC
i believe seomoz is also written in MVC, cant remeber what tipped me off to that maybe some one from SEOMoz can confirm

MVC also leaves very clean code, no postbacks or viewstate to clog up the code

The Microsoft IIS SEO Tool Kit
I am yet to find a site that does not have a pile of errors, I get all my sites free from violations, this gives me a head start (how big that head start is is debatable)

If your technical side is not perfect all your SEM is discounted. Its like fishing with holes in your net.

good to hear that i am not alone.
I can avoid a job day after day after day. but once im on my way, the sun comming up tells me its time to quit

Are all pages being indexed?
How do the rank relative to each other, is the home pahe ranking well?
playing with redirects is temping fate i think,

I agree, trying to target many locals may stuff you up.

I follow the format in google places, but i would think SE's ae smart enouth to pick up most addresses

10 Main St
Suburb City State Post code
Country

Lets say you had a domain xyz.com, and you had 3 peole tbhat had their own blogs
tom.xyz.com
dick.xyz.com
harry.xyz.com

wel then search engines may see this as non related sites

but if you had a site clothing.com

and had shirts.clothing.com
and shorts.clothing.com
and pants.clothing.com
then search engines proobably will see them as the same

to help to make sure you are seem as one in the same site, do planty of linking betwen sites, haveing all your images and stayle sheets in teh parent domain will also help search engines see that you are one large site.
try to make the links both ways,

i have done this on a few sites and i have had good results

The url
length should not be ridiculously long, I think 255 chars in the safe limit.

So long as
you keep in that it’s ok, but if you have a long bread crumb trail, your page
is probably many clicks from the home page also and this is bad.

Many people
think that the problem is having pages deep in the folder structure, but it is
not, it is the amount of clicks from the home page that is the problem