Hello!
I'm not on the Airbus, but on the Boeing, but assuming basic aerodynamics are not much different, here are some pointers I've picked up. They may or may not be applicable to you.
1. The VNAV/computer path is only as good as the info you put into it. It is only correct when you actually fly what's in the box, which is practically never.
2. If you are in doubt if you are high or low, then you are high.
3. There are only two ways to unfu*k number 2: go fast and clean (like a brick), or slow down, dirty up (like a leaf). The first one is better if you are far out, the latter is better if you are close in.
4. If you need to eyeball it when being vectored on downwind, use the range-to-altitude arc to plan to be abeam the field at twice your platform altitude if at normal descent speed, or add up to 2000 feet if you have already been slowed down.
5. If you are number x in sequence, plan 1500'
pr plane ahead. So if you're number 6, about 9000' isn't too far off the mark. Use a lower figure (like 1000'
pr plane ahead) for denser airspace.
Good luck!