There are a number of things that can be done to reduce the likelihood of corrupt activities. None of them is guaranteed to work for all people. There will always be some people who end up corrupt. That said, let us look at a few approaches to reducing corruption.
Give them decent pay. One cause of corruption is economic need. There will be times when people take bribes and such because they do not get good salaries. You can never pay people enough to guarantee that they will not be corrupt, but decent salaries can help to make corruption less likely.
Have harsh penalties. There is a degree to which threatening people will work. If you have harsh punishments for corruption and you publicize those punishments, you might deter people. This is particularly true if it appears that people who act corruptly are likely to get caught.
Training. You can give people training on how to avoid corruption. If workers know the kinds of situations in which they are likely to be drawn into corruption, they can work to avoid those situations. It is easier to avoid wrong behaviors if you are to some degree forewarned about them and if you are trained in strategies for avoiding them.
Esprit de corps. One thing that prevents many people from becoming corrupt is the feeling that they do not want to let down their comrades or their profession. If you have an emphasis on creating this feeling, you will put more pressure on people to behave properly so as not to disgrace themselves in the eyes of their comrades.