I just noticed you also asked for hints.....
1. Don't leave the bulb in the holder once it has discharged...if you forget it's in there it goes icky after a few weeks
....voice of experience
2. Pure cream seems to work better than thickened
3. Distribute the gas by gently rocking the whipper 180 degrees from side to side. Don't shake it violently ....again the voice of experience. Do int about four to six times
4. Always test it on something first. A hand works well cos then you can lick the cream off....I'll not recommend who's hand :p
5. Don't forget that there is cream in it and bury it at the back of the fridge for two months. The gas will help extend the life of the cream....but not by that much....and they are not the easiest thing to clean.
6. Always at least rinse the nozzle under hot water if not cleaning immediately. Solid cream is revolting to try and get out of a nozzle