First of all the answer is simple "Very carefully". But to get real
let me give you some tips.
There are many types of forklifts.
Floor Jack Motorized. Easy to move controls on the handle, Push down to raise up. Left is left right is right unless you go backwards then the opposite.
Light Forklift: Used to lift loads under 1000 pounds.
Your foot pedals start it and stop it. Shift to reverse.
Here is where it gets trickey; You usuaully have two sets of levers, one set lifts the forks up and the others control the tilt.
The trick is to make sure as you lift an item that the tilt keeps the item from falling off the front of the forks. As you go up the forks level out and if the load is not fully back on the forks it could slip off.
Before picking up your first load you should practice with any empty pallet lifting and leveling so you get a feel from what the forks will do.
Older models have been known to lose hydrolic power and may not be suitable for heavy loads.
Then there is the RT (rough terrain). This baby is used for the heavy loads and where the surface is uneven or slippery. The tires are bigger and the forklift will run faster.
It is reccomended that you have a little experience before using it.The controls are much the same as the lite forklift in the way you use them.