Whether rents are rising or falling depends entirely on the city and the moment, so check the current temperature rather than assuming: the local property portal's listing volumes and price trends, plus recent news about the market and what expat groups say about competition for viewings, tell you within a day whether you're in a landlord's or tenant's market. That diagnosis decides your strategy, because negotiation is entirely leverage-dependent.
In hot markets with multiple applicants per viewing, haggling on price mostly loses you the apartment; your edge there is speed and completeness, showing up with documents ready and committing fast.
The levers that work: offering a longer lease, since vacancy risk is the landlord's real cost and certainty is worth money; several months paid upfront, especially useful for foreigners without local credit history; flexible or immediate move-in dates that close a vacancy gap; and polite, specific asks referencing comparable listings rather than vague demands.