Identify product or service, (New product or after market modification ?)
Trademark, copyright or license as needed
Business plan
Financing
Set up ( facility, staff, insurance, tooling, prototypes )
Marketing
In my opinion the most difficult part of the whole thing is coming up with the original idea .
Something that will be greeted with "hey, I could use one of those" instead of, Ho hum, another bolt action, AR, 1911 etc" .
Services are a little easier, how ever you need to study your market, why isn't there a good gunsmith in the area ?
Are there no good gunsmiths around here, or did the last one starve to death ?
If he starved to death was it because there was no market, or was he not reaching that market ?