The most important about hatching is the type of data required and also quantity of data required per inject.
For example a guilmon mercenary digiegg
You will need DragonLow Class data for injection and each injection requires 10 DragonLow Class data.
To begin hatching, first you need to find an incubator. It can be found in Dats Centre, Yokohama Village and other various place.
Now, first, register the mercenary digiegg that you want to hatch into the incubator. Then, you can start injecting data to hatch the mercenary digiegg. To be able to hatch a new digimon, the mercenary digiegg must at least inject successfully for 3/5 times, maximum injection is successfully injected 5/5 times. An unsuccessful injection will result in breaking the data injected or even destroy the digiegg.
The number of successful injection will affect the digimon's size. For more information on digimon's size, please refer to All about digimon size.
Cash digieggs
Sometimes, you will see someone is selling this kind of digiegg in their store.
This is a cash digiegg that bought from cash shop. Depends on the level and class of the cash egg, the pictures above is a ExV - mon digiegg level 4 ( champion ), it means that the digiegg will 100% successfully hatches to 4/5 ExV - mon without the need to worry about breaking the digiegg, when the egg is hatched, it will unlock evolution until champion.
Never remove your digi-egg for its incubator, unless it is a 0/5. If you remove it, the digi-egg will disappear forever. However, you can press cancel button when you are short of data or you want to inject data later, the digiegg won't disappear instead.