Most important in my opinion is to keep a thorough log of improvements made to the property. Unless logged - many of these improvements fall through the cracks over the years. These expenses add to the basis of the property and reduce gains upon sale.
Serving Maryland, D.C and Northern Virginia
Obviously, you should consult your accountant or a tax attorney but as far as I know a 1031 exchange may work for you - that's where you purchase a similar property with the profit of the sale of your current investment. The only other way I know of would be to make the investment property into your primary residence. Again, as far as I know you have to live in a property at least two out of the past five years to qualify as a primary residence. If you haven't listed the property yet and are not currently working with a real estate agent, I have many properties in Queens and Long Island in my ten years in the business.
Century 21 Princeton Properties
If you do not want to purchase another property, talk to your accountant about the many expenses and circumstances that can help minimize tax liability.