Jbro129

A short way to answer that is to...
#1 Try to disable or temporary stop server syncing (example would be in clash of clans and making the server sync popup not show up so it doesn't force an app restart.)
#2 Once you have disabled it, try to find a way to get whatever it is you want. Inapp currency or level or whatever it is that you want.
#3 Make the game think that what you have is legitimate so you can then apply your modded currency or whatever you are modding to the server. 
A tip when modding in app currency is to make the game think you got the currency through in-app purchases. Another way is to spoof in app purchases so you can get the reward without paying, which takes more skill, time, and effort .