Small? Specialize and get billing, taxes, legal and ERP covered. Legal and taxes are other people, billing an ERP can be done with online tools like FreshBooks or small to midsized softwarepackages like Lexware.
What practices you need is up to you - especially if you code alone.
It also depends on the code you write. If it's just custom ABAP scripting for a handful of clients at a time, point and click testing and a few manually checked testpositions ought to be enough.
If you want to deliver software to a wide range of customers, perhaps even online, with demo-versions and stuff you *have* to have your pipeline standing, even and especially if you are alone. You want to be able to compile and deploy a hotfix wih a mouseclick.
Ask yourself: if the worst possible szenario happens with my software, will I be able to fix it inmediatel? If the answer is yes, with a few night-shifts and my leet Google searching skill I ought to manage somehow - that's OK. If the answer is no, compiling for XYZ takes days of time each time around - then you're doing it wrong and need to automate your process (more).
As for the business itself: Specialize in a field and a subset of that. There is no other way you can keep up with the big boys as a small shop. ERP, Web, Embedded, DB, etc. They all have their ups and downs and each have countless subcategories you can specialize in. Do it! Do not look left or right, unless you don't have any customers in the current field.