Tax write-offs for a business that does not have any income and only losses?

I am incurring costs for education and building my new start-up business. But if my business does not have any income and only losses for the first year or two, what am I taking the write-offs against? Am I wasting my time in keeping and tabulating the receipts for everything? In sum, do tax write-offs for business-related expenses make a difference if your business does not have net income? Can the tax write-offs from a previous year perhaps reduce taxable income in the next tax year?