You can't negotiate without knowing rent prices for apartments in your building. Your landlord is probably advertising apartments online that are very similar to yours. You shouldn't pay more than the advertised prices -- the same amount a new tenant would pay.
You also should know rent prices for similar buildings in your neighborhood. You can quote these to the leasing agent as an implicit threat that you'll move out if you don't get the right price. This will also give you confidence that you have options if you can't negotiate a fair rent for your current apartment.
If current prices in your building or in your neighborhood are lower than what you're paying you may be able to negotiate a LOWER rent next year. There is no law of physics stating that rents can only go up.
Evidence can be compelling. You can print prices from the website or download them to a file using a PDF screen grabber like the "Save as PDF" extension for Chrome or Firefox. Sending prices to the leasing agent is a powerful way to show that you are not to be messed with.
Knowing comparable prices market doesn't guarantee a good outcome in your negotiations but it gives you a much better chance of getting a fair rent.