Honestly I think you are asking the wrong crowd. 95% of the members here don't want anybody else touching their vehicles. I honestly let about 2 shops in the state touch my stuff. The only reason being that they have been family friends for decades. If I take something in there, they let me back in the shop, help them with the work, let me work on something else while they are working on my stuff, give me a great deal, I can stop by and BS with them while they are working on somebody elses stuff and help them work on it, etc.
As far as the diesel scene goes, you have Elite, Rockin S, then Haller's in WY to compete with. In my opinion it will take you years to get references that would amount to anything over them. Your average Joe Blow gets on the internet and asks for a good diesel shop in Colorado, and those are the names that come to mind without a thought. The gas market will be the same way.
I've toyed with the idea for several years, because it is what I would love to do. So think about what makes those big name shops popular? They have some bad ass vehicles that make it to events all over. Elite has some trucks making crazy power all over the country. Rockin S has Rocky winning the DPC. Haller's has some trucks making tons of power. Their vehicles are good enough to get acknowledgment all over the country. If your baddest vehicle is running 15's at the track, people aren't going to be too interested.
So to get quick recognition and a client base, my suggestion is to, before you spend the money on getting a shop going, build some bad ass vehicles, diesel and gas...get them out on the drag strip all over the country with some big stickers on them, get them on whatever venues you think you are targeting, shows etc...Start to get a client base built up working from home or wherever before investing in a full on business. Take some losses on some sponsorships on vehicles you see that will help get your name out.
To answer your original question, if you are going to start up a shop and want to make a good impression, don't hire Jethro from the trailer park. Keep your place clean. Make every single customer happy for the first year or so, no matter what. Make everyone who comes in the door feel like they are getting a deal, even if you give them a slightly inflated quote to begin with, and then cut it down, they will feel like you are working with them. Advertise the **** out of your business. Don't expect to make money for the fist couple years. Try to come up with something unique to offer, that will draw a customer base in for that particular thing. Pick a location that is easy to find. Not something that is "turn right on so and so, then hang a left around the dumpster, then make a 140 degree turn and we are the shop with the glass door". There is a bunch of other little things that will help that I can't come up with right now. I do have a distributor connection that can help you with stocking big name brands and such if you are interested.
If you take it on I wish you luck, and will stop by for sure.