The successful sharpening of a cleaver depends on the style. Meat cleavers are distinctively different, therefore, sharpening techniques also vary.
A slightly used meat cleaver (European steel)
This style of cleaver generally has a very basic bevel, with a large thick blade. Since it is still sharp and doesn’t need intense sharpening, try using a 300 grit Japanese whetstone.
Sharpen the meat cleaver from the heel to the tip at a slight angle, being careful to follow the same profile. Repeat the same motions with the other side of the cleaver for it to be evenly sharp. Wipe down the cleaver before use, and rinse off the whetstone to remove the metal particles from the cleaver.
An old blunt cleaver (European steel)
For an especially old cleaver, consider profiling it first on a rough stone before sharpening. Unless the cleaver in question is very thick, sharpen it at a 22.5-degree angle. You can achieve this by estimating a 45 angle and then halving it. Sharpen the cleaver symmetrically to attain a bevel width that is symmetrical on both sides, a trick that will increase the durability and lifespan while making the cleaver easier to steel.
When the bevels are even and flattened to your satisfaction, proceed to sharpen your cleaver again, this time at around 30 until you successfully burr both sides the deburr.
A 30 cutting bevel is sufficiently able to withstand constant use. The edge should not be too wide to prevent any chances of it wedging. You could also opt to use an electric grinding stone to edge and hone you meat cleaver, and finish off on regular stone.
Meat cleavers do not need to have a razor sharp edge especially if you are going to do a lot of chopping. This is because a thin edge will end up folding, ruining your cutting. A recommended angle for sharpening meat cleavers is usually between 30-35.