Veil

Minting zerocoins, by default is automatically done in the Veil core wallet.
You can set the default amount on the minting page and in the Veil configuration file.

Using the Zerocoin minting page in the graphical user interface

The "Zerocoin minting" page can be found by clicking (or tapping) the Settings (gear icon) and then under Options, "Zerocoin minting".

If you tried to mint some zerocoins on the Minting page and got an error, and the Veil that you want to mint is currently in the basecoin balance please remember to tick the box that says "Use basecoin". 

If there is enough Veil in any of the other individual balances, and the 'use basecoin' box is not ticked the minting process will choose firstly from a sufficient balance in RingCT, if not sufficient in RingCT it will mint from the CT balance if that is sufficient. If neither are sufficient it will tell you there is not enough.

As the hint in the amount box says, the amount should be a multiple of ten, but this is really only if you want to mint some tens. To be more clear, the amount should be a multiple of the zerocoin denomination you want to mint. If you want to mint 1000 denomination zerocoins you should choose any multiple of 1000 up to 9000. If you choose 13450 it will mint one 10000 and three 1000s four 100s and five tens. The default of minting ten denomination zerocoins in the current market and with the current Veil supply is not a popular choice and it is commonly recommended to set the default automatic minting size (in the left section of the screen) to either 10000 or to 1000.

Finally, you should make sure that the balance in whichever coin category has the amount that you are trying to mint, and allows for the 0.01 Veil per zerocoin being minted. For example, to mint three 1000 denomination zerocoins will require 3000.03 Veil. To mint the 13450 in zerocoins used in the example above is minting thirteen individual zerocoins and would therefore require 13 * 0.01 Veil for fees, so your balance in one category would have to be at least  13450.13. To mint one 10000 would only require 10000.01.

Using the Debug Console

Open the debug console by choosing "Advanced options" on the Settings page, or do the command in the equivalent Command Line Interface terminal. Minting amounts and fees follow the same rules and suggestions as written above for the graphical interface. Minting from basecoin simply requires adding " true" to the end of the command which is an answer to the question "use basecoin?"

mintzerocoin Amount

For proper privacy it is strongly recommended to mint from RingCT. You can see your available balances by

getbalances

listzerocoinamounts

mintzerocoin 3000

For further information on staking statistics and results, entirely according to chance and probability, please check https://veil-stats.com/charts