This question gets asked every day at WHT:
Running a Web Hosting Business - Web Hosting Talk
Lots of good information and advice there.
Few ideas from an old hand:
Starting locally is a good idea these days as the global market is heavily saturated. You should invest in some
SEO to target some local terms like "web hosting Idaho" or "Boise Web Hosting" etc. Should be quite easy to rank for those terms quickly as the competition will be low and probably not
SEO-savvy.
Secondly, work with your local Chamber of Commerce. You'll get great networking opportunities and they might even give you some free business training where you meet even more people. I have a friend that did this (who became an HN customer) and his business exploded after working with his local CoC.
You should work on becoming "The Hosting Guy" in your home town. Maybe team up with a local web design firm so you can provide a complete "web" service to local business (design, hosting, maintenance). But even with just a hosting service you can still become the go-to guy in your town. The postcard thing won't work as it's too random, too amateur really. Get some proper flyers done up, post them in stores, billboards, anywhere that will have them. Do you have a local newspaper in town that comes in the morning sometimes with flyers? If so find out how to get your flyers into these papers (much better than mail-dropping).
Work on a presentation that you could give to local businesses. Have a small CD/DVD made up with a presentation about your company, screenshots/video of your site, explanation of what you offer. Go into a photo studio and have them take a professional video of you giving an introductio and/or conclusion that can be added to the presentation DVD. Show people why they need stable hosting (and web design if applicable). Mass produce it on your own PC, make a nice cover. Get a brochure done up (something nicer than a flyer) - you can get a web design firm to do some nice stationary designs including envelopes. Bundle up the DVD, Brochure, Introductory letter in a nice envelope, go around town every day for a week dropping your envelope off with a few words to all the businesses. Nice thing about this approach is that you don't need a big pitch, let your presentation do the work. Your envelope might be lying on someone's desk for months before they open it, or maybe they'll look at it, file it and in the future when they have a need your name will come to mind.
Yes, you will need to spend money if you really want to establish a successful company but compared to most business start-ups the above things are incredibly cheaper - talking a couple of grand really. I would advise that you don't be scared to spend some money on a project you COMPLETELY believe in. If you see no possibility of failure in your future you will succeed as you'll have the drive and determination to make it work. There will be tough times, every start-up has them but if you have the belief, the drive, the tunnel vision that you can't fail, then you won't fail.
So start locally in Boise, and if the approach works you can expand into other towns and cities in Idaho (I'm sure there most be) and as you build a client base you'll find word of mouth will bring you most of your clients.
Hope some of this helps.