A trick my German professor gave us to remember cases and prepositions
(TEACHERS HATE HIM because of this ONE WEIRD TRICK!) I couldn't resist.
He explained that certain prepositions almost always take certain cases. We've only covered accusative and dative (which luckily seems to be the order here on Duo!) and I find it super helpful.
For Acc. there are 7 commonly used ones:
Gegen Durch Fuer Ohne Um
For Dat. there are 9:
Aus Ausser Bei Mit Nach Seit Von Zu
He gave us a couple of melodies that match. For Acc. you can sing the tune of "London bridge is falling down," as "Ge-gen durch fuer, oh-ne um, oh-ne um, oh-ne um." Und so weiter.
For Dat. you can use the melody of Strauss' Blue Danube Waltz. "Aus ausser bei mit, nach seit, von zu." (Because I realize that there might not be many music nerds out there, here is a link: https://youtu.be/_CTYymbbEL4 Everyone has heard it before, and the part you're thinking of is probably at 1:33)
Hope this helps!
Good suggestion to use melodies for learning! You might want to edit the spelling in your post, though. Außer is spelled ausser if the ß is not available on your keyboard (always replace "ß" with "ss".) This is important as it affects the pronunciation: ß and ss indicate a sharp s and a single "s" is pronounced like our "z". Also, it's not "seid" but "seit".
Press and hold down the ALT key whilst typing:
0196 for Ä
0228 for ä
0214 for Ö
0246 for ö
0220 for Ü
0252 for ü
0223 for ß
NB: You must use the numbers keypad and not the numbers above the letters. Also NUM LOCK must be on.
In primary school German lesson we learned the following rhyme "Mit, nach, von, zu, aus bei fordern stets Fall drei" and that is indeed true, these prepositions are always used with dative case.
I can still add prepositions with Acc. or Dat. together - an in neben auf über unter vor zwischen I think its all - now it was my memory with 30years remembering
To Twinkle Twinkle Little Star...Durch fuer ohne um und gegen, are accusitive preopositions.