First of all, keep in mind that the temperature and humidity level of the room has to be steady and consistent. If you keep them constant throughout the year, your organ will be in much better shape.
The next thing is to maintain the reed stops regularly - especially before important performances. Whenever you have to play in public with reeds, try to tune your reeds. This way your old organ will sound much better.
Finally, whenever you encounter a sticky note or a cipher, you have to go inside and fix it. Keep in mind that sometimes you will need screwdriver and sometimes you will be able to regulate the action with your fingers.
However, be very careful because that is an old organ and especially if that is a historical organ. Every adjustment you make will be very important so your every movement has to be precise, very small and elegant.
If you are not careful with your fingers, you can produce much damage to the organ and later a major restoration will be needed. It's better to consult an experienced organ builder who has a license to work with historical materials than to do it yourself and cause problems in the future.
Apply my tips when you have to maintain an old instrument and your organ will be in good shape throughout the year.