Hi I'm a forklift truck instructor.
When raising your forks to take a load down, stop when the forks are at your eye level and looking along the top edge of the forks adjust the tilt control until the forks are level, then continue up to pallet entry height and insert the forks, do not adjust the tilt again until you have entered the pallet and raised the load.
When placing a load onto a stack or rack, use the same procedure as above, only this time look along the bottom of the pallet to judge if the load is level, once you have placed the load apply a small amount of forward tilt to free the forks if required before withdrawing them, this slight forward tilt upon placing the load is sometimes required when placing a heavy load to compensate for the fact that the forks will spring to a slightly tilted back position when a heavy weight is removed from them, even though the load was level when you checked it at eye level.
Hope this helps.
Google "sumolevel" It is a great product for levelling your forks and particularly at height.