What steps did Hitler take once he took office in order to prevent opposition?
Through the formation of a One Party State and the elimination of the SA.
In 1933 the National Socialist (Nazi) Party came to power in Germany when its leader, Adolf Hitler, became Chancellor.
One of the first steps, to ensure that no opponents could interfere, was the introduction of a "one party" structure excluding from the Parliament (or reducing) the presence of other parties representatives such as communists, socialists, social-democrats, etc. sometimes even physically attacking them.
This was possible and done through a clever activity of propaganda accusing the "decadent parties" to endanger Germany with their actions and so not being worth to represent the people in parliament:
the communists because connected to Soviet Union and so accused to be serfs of Stalin and trying, with their actions and ideal of revolution, to handle Germany to him (this was particularly appealing to the rich and industrialists);
the socialists and social-democrats because guilty of always quarreling in parliament without reaching any conclusion or solving problems and leaving Germany in a state of defenseless and prostration as after World War I (this was particularly appealing to the masses left enraged after the capitulation and induced to think that they were betrayed by the weak parties in Germany).
But Hitler didn't have enemies only in other parties.
The Nazi paramilitary faction of the SA (SturmAbteilung - Action Squads) lead by Ernst Rohm represented a big danger for the political ambitions and position of Hitler. In 1934 Hitler unleashed the SS (envious of the power of Rohm and lead by his antagonist H. Himler) in a purge of the SA. During the Night of the Long Knives Rohm was arrested and murdered and countless other SA members were eliminated throughout Germany. After this night the SA became a kind of a folkloristic parade formation only used during Nazi celebrations and Party rallies to remember the good old days of Nazi history.
In general, opponents to the Nazi were excluded from prominent position and their names, occupations, skills and origin recorded in lists that later were going to be used to round them up to be sent to concentration camps and….disappear!
These actions were implemented even at a person to person and local basis. I remember an anecdote of a German friend of my father (that witnessed that period) that told us this story:
Throughout Germany functionaries of the government were “censing” the owners of radios (at that time comparable, as influence, as today’s TV) asking also if they wanted to change their “old and battered” sets with a new one completely free supplied by the state (obviously this new and free set couldn’t really get ALL the radio stations…its frequency selectors were set!). The majority considering the kind of “mafia” stile request and imagining the consequence of a refusal obviously accepted the new set. When the functionaries met someone that didn’t want to change his radio simply and friendly told him: “Sir, could you give us your name, address and occupation….only for the record, you know…”