On the low-end you've got cpanel resellers, on the middle-ground you have people who buy hardware and stick it in racks in other peoples' data-centers. On the high-end companies build, assemble, and host their own kit.
Really it comes down to identifying your ideal user and marketing, advertising, and cutting costs.
Small hosting companies usually promise "personal support", but of course the reality is that support is timeconsuming if you're doing it alone, and expensive if you have to hire decent sysadmins.
Actual specifics will depend on where/what you're doing. Do you have your own hardware? Your own links? Your own AS, etc? Or are you reselling something from somebody else?