First thing I would suggest is read the manual front to back, I never read manuals but with a digital camera you have to. What model camera do you have?
No flash ever! Most tanks have nice light so use it!
If you want to do bog standard pointing and shooting use the auto functions, the camera will do most of the work
If you’re happy with 10% of your pics then your not doing bad anyone doing Digital photography will take thousands of photos and bin a lot of them, its digital so it costs nothing.
I would suggest using a tripod or a monopod these will cut down on camera shake weather you’re taking pictures or filming.
Make sure you have your quality settings at maximum! Its digital so it costs nothing
Night time is best when the room is darker as you don’t have to worry as much about reflections on the glass.
Here is the last pic that I took that im happy with,
Every image you take is different so they all need different settings if your using manual mode it takes a bit of time to study and learn but if you have the interest its worth doing
If you can post a few images we might be able to tell you what would help