• Will you be using it indoors, outdoors, or both?
• What surface will it be operated on ?
• How large and heavy are the typical loads?
• How high do the loads need to be lifted?
• How much room do you have to maneuver? How wide are your narrowest aisles?
• How many hours per day will it be used?
• What fuel type best fits your application?

Forklift capacity: Know typical load weight and size.
How heavy and what size are your typical loads? Forklift trucks are rated according to how much weight they can lift, starting at 3,000 lbs and going up to 35,000 lbs and more. 3,000-, 5,000-, and 8,000-lb models make up the bulk of the market, with 5,000 lb forklifts as the industry standard. The size of your typical load will affect the capacity you need.
Forklift capacity is usually based on a 24-inch "load center," meaning that the distance from the center of gravity to the sides of the load is 24 inches. The easiest way to think about this is that a forklift can only lift its maximum weight if the load is a 4 foot cube. If your loads are unusually long or high, the forklift won’t be able to safely lift as much. Knowing the typical dimensions and weight of your loads will allow you to work with sellers to determine the exact capacity you need.
Also consider variation in your loads. If you constantly produce identical pallets of products, you know exactly what capacity you need. However, in a more mixed environment, or one where the load size changes over time, you may want to buy a truck with more capacity than you need currently to make sure it gets the job done now and in the future.

Consider where you plan to use your forklift
How high do you need a forklift to lift a load? If you primarily use forklifts to load and unload trucks, you may not need much height; if your warehouse has shelves 30 feet high, your forklift will need to reach them. Unlike load capacity, your height needs are unlikely to change over time barring new construction or major renovations. Buy for the height you need now. In a warehouse setting, the size of the lift truck may be an issue as well. Standard lift trucks need aisles that are 11 feet wide or larger to be able to operate and turn around. For aisles that are 8 feet to 10 feet wide, you will need a narrow aisle (NA) forklift; for aisles down to 6 feet wide, you will need a very narrow aisle (VNA) truck. These narrow aisle trucks have forks that are turned at a right angle, so they can drive straight down the aisle but pick up loads to the side.

Tire selection: What surface will it be operated on?
Cushion tires: Cushion tires made of solid rubber work best for internal applications. Electric forklifts designed for inside work typically have cushion tires.
Pneumatic tires: Pneumatic tires inflated with compressed air cost more than cushion tires, but make a better choice for outdoor work. For heavy-duty lifting outdoors on uneven terrain, you'll commonly find gasoline or diesel forklifts with pneumatic tires.
Solid pneumatic tires: Solid pneumatic tires are ideal for outdoor environments where there's a high risk of popping regular pneumatic tires, such as lumber yards or recycling centers where glass or nails can be scattered. Solid pneumatic tires combine the solid-rubber construction of cushion tires with the rough terrain capabilities of pneumatic tires, and typically cost more.

How long you'll use your forklift each day.
Many dealers offer both new forklifts and used forklift trucks, so you can compare prices easily. Buying used forklifts can save you quite a bit up front, usually costing around half the cost of a new forklift. As a general rule, businesses that use forklifts for more than four hours each day should invest in new forklifts.
If the forklift will be used only a couple of hours per day, you can probably benefit from buying a used forklift. When the dealer gets a used forklift back at the end of a lease, they usually recondition it with a new paint job, new tires, a thorough engine tune-up, and any other mechanical repairs that need to be made, so you can feel confident in the condition of the truck. "As-is" forklifts can save you even more money, but may have original paint, worn tires, and generally not be in the aestetic shape you would expect.

Forklift Fuel Type
You'll find two main types of forklifts: Electric forklifts powered solely by an on-board battery and internal combustion (IC) forklifts, which use a traditional engine that runs on one of several types of fuel. In most cases an electric forklift will be more expensive than an identically-rated IC lift. Operating costs per hour are critical to determining the real cost of your forklift. This includes the cost of fuel, maintenance, supplies like oil, batteries, and filters, and the time required to take care of the truck.
Electric forklifts
Electric forklifts are well-suited for indoor use and use in well-paved parking lots (not in the rain). They're powered by large, heavy lead-acid batteries — the same kind found in your car, but considerably bigger and more powerful. Electric forklifts have several advantages.
Zero emissions: Electric forklifts produce zero emissions, an important consideration if you plan to use your forklift indoors. Of the internal combustion models, only propane-fueled lifts can be used indoors, and they require very good ventilation. Gas and diesel-powered models can’t be used inside at all.
Low fuel cost: Although electric forklifts have a higher initial cost than internal combustion forklifts (new electric forklifts can cost 20% to 40% more than similarly rated IC forklifts), they have a lower cost per hour of operation.
Quieter operation: Electric forklifts produce less noise than IC forklifts, a big plus indoors.
Long lifespan: Because electric forklifts have fewer moving parts and are often used in cleaner environments than IC forklifts, they also tend to have a longer life span.
Electric forklifts have no fuel storage requirements and the batteries typically provide enough power for one standard eight-hour shift, which translates into five or six hours of constant usage. Keep battery downtime in mind. Charging a forklift battery takes eight hours, plus eight hours of cooling time before it can be used. Due to this slow charging speed, if you need forklifts for two or three-shift operations, you will have to buy extra batteries so you can always charge the next one. You'll also need a battery charging station. Chargers should be located in a dry, ventilated, and temperature-controlled location. If you have multiple batteries, you will also need special cranes to change them.
Internal combustion (IC) forklifts
Internal combustion (IC) forklifts can handle the largest loads and are the only choice if you require greater than 15,000 lbs capacity. They typically stand up to certain types of abuse better than electric forklifts — specifically, using a forklift to push or tow loads, instead of lifting and driving — and usually have better acceleration and top speeds. IC forklifts have a lower initial price point, but cost more per hour to run than electric forklifts.
Forklifts with internal combustion engines run on a variety of fuels: gasoline, diesel fuel, liquid propane gas (LPG), or compressed natural gas (CNG). For indoor/outdoor use, duel fuel systems are available that let you switch between LPG and gasoline. You can refuel internal combustion (IC) forklifts on the fly: simply fill them up at a gas pump or load on new LPG canisters and your forklifts are ready to continue working in no time. Of the types of IC engines, fuel costs generally are highest for gasoline and lowest for diesel, with LPG in the middle. Fuel costs vary considerably from state to state, so you should investigate this cost in your area before deciding which option is best for you.
With some IC equipment, you will have to buy refueling equipment. For example, gasoline and diesel fuel require you to have storage tanks and pumps. LPG requires only space for spare tank storage, which is usually managed by a propane vendor. The choice between gas, diesel, and propane is often made based on existing vehicles and equipment.