The answer to your question is not simple, you asked a broad question. Depending on what you plan on lifting, ATV's, cars, trucks, or tractor trailers this will determine what you need to lift it. If you are planning on lifting cars, then you will need two hydraulic pistons rated at, at least 1.5 - 2 tons. You would make a simpler scissor lift. But to make a traditional lift, you will need very large (tall) hydrualic pistons have approximately a 5-6' range to lift the car up enough. Also, you will need hydraulic pumps and fluid that can support the kind of load needed for these pistons. Then you will need to make a housing to encase this all in and you will need to make a lift arm mechanism. This will need to be very strong, high carbon steel since it will act as a cantilever beam. 4 arms need to be made that swivel out to support the car. I've listed a couple sites below that show them, the scissor lift would be easier to make but not as useful since the car's tires actually ride on them and usually to do any kind of maintenance, the tires need to be removed for doing the brakes, struts etc. You can buy a whole lift kit for only $1375.00. You might want to think about just buying one instead of making one.
