One method that works for many small businesses is to have a calendar devoted only to deadlines and other events that may affect the business. It can have tax dates, equipment repair schedules, payroll payment schedules, and even dates for reconciliation of accounts in it. Note everything on it that affects your business so critical deadlines don't slip by while you are involved with the day-to-day running of your business.
At a particularly busy time in my life I used to also note on my master calendar critical events in my kids' lives in green so that I would not miss something like a school play just because I had not planned far enough ahead for filing my taxes. The green events inspired me to get the other deadlines completed early so that I could be relaxed and truly enjoy the special moment with my children.
Besides a master calendar, the other critical component is good filing. Information is no longer information if it cannot be retrieved when it is needed. The two most common types of filing systems are alphabetical by category or chronologically by date. Many people file chronologically within category. Different types of systems work for different types of businesses and different types of people. Feel free to experiment a little while you still have a relatively small filing system.
Some types of records occur infrequently, but need to be kept permanently. Items such as corporate records, licenses, permits, insurance forms, bank accounts, rental agreements, equipment leases or other legal forms need to be filed somewhere they can be accessed quickly when they are needed. Other categories such as suppliers, customers, employees, correspondence will need to be updated frequently, preferably daily, so it may be desirable to split them off in a separate file. While a good filing system is important, don't fret too much about setting it up perfectly at first. You will find it evolves over time. The primary issue is to set some system up and to form the habit of keeping it up regularly. Then, try to revisit the system setup itself at regular intervals to see if there are better ways to organize it to ease the flow of information.
One last question that is always asked is how long do I have to keep business records? Receipts, cancelled checks and other documents that support some reporting requirement need to be kept until the statute of limitations expires on that report. For U.S. federal taxes that is three years from the date the tax return was due or filed or two years from the date the tax was paid, whichever is later. Some records should be kept indefinitely. Records in this category are property records, corporate records or insurance documentation. Employers must keep all employment tax records for at least four years after the tax is due or paid, whichever is later.
For those records that you can't decide about, consider how difficult they are to replace. Most banks microfilm checks and you can get copies from them with adequate notice. When in doubt, check with the institution to see what their policy is on recordkeeping. Their policy might give you good guidelines for your storage. The bottom line is that you want to store as little as possible, but you do want to have records available when and if they are needed.
Perhaps you can now see why there are people who make a good living just setting up recordkeeping systems for businesses. There are a lot of factors to consider. I always recommend you do it yourself because it is your system and you will be the one who has to maintain it. If you do not tend toward the compulsive end of the spectrum, however, make certain that you hire someone who is. The professionalism of your business operation is going to be dependent upon these systems. Your financial systems are the underpinnings of who you are as a business. Make certain they reflect the quality you want your business to project.