If you are conducting business then definitely open a business bank account for that. The primary reason is simply to have a separation of concerns.

It's a huge hassle to have to have sort through a personal bank account to find all your business items when you need any kind of financial reporting.

I don't have 4 distinct reasons to give you aside from the one big reason and that is that it just makes keeping track of business revenue and spend a lot easier.

As far as tax deductions go you basically have a categories you can file expenditures under that qualify for deductions. Just add those all up for each category at tax time and deduct.

Of course you will want to discuss the finer details of that with a business tax professional/CPA.