Germany is a generally very accessible country from a ticketing perspective. All clubs have an online ticketing system (even for large clubs in the 4th/5th divisions) and most use the same system. Ticket sales typically open between 2 and 4 weeks before matches.
The majority of clubs offer resale on their ticketing platform, so opportunities can arise right up until matchday.
Most large clubs have an annual "membership" system that brings benefits, notably priority access to ticket sales.
For major clashes or derbies, it is often necessary to be a season ticket holder or member to access the sale.
Match tickets are not personalised in Germany.
Find ticketing information for each club on each stadium's page.