The accusative only affects masculine nouns:

m	den	einen	keinen
f	die	eine	keine
n	das	ein	kein
p	die	eine	keine

PREPOSITIONS which are ALWAYS followed by accusative:

bis	until
durch	through
für	for
gegen	against
ohne	without
um	around
entlang	along

PREPOSITIONS which are followed by accusative IF moving TOWARDS the object:

in	in/into
an	at/by/ on (vertical surfaces)
auf	onto (horizontal surfaces)/on/at
vor	in front of/outside/before/ago
neben	next to/beside
hinter	behind
zwischen	between
über	over/across/about (concerning)
unter	under/among/beneath

VERBS which are followed by accusative: haben, kaufen, sehen, suchen.

SEIN cannot have an object, so cannot be followed by accusative.