1. Make characters on game worlds that are close to the place you play from
Tibia has currently got servers in three locations: North America, South America and Europe. Make sure to pick a server that is the closest to the location you play from.
2. Verify that "Optimise connection stability" setting is enabled
This setting can be found directly in Tibia, under Options -> General -> Optimise Connection Stability and is enabled by default. The exact algorithm or details on how the connection is improved are not known, but it seems to improve the stability of the connection a bit. Having this enabled can increase network traffic.
3. Download and install Leatrix Latency Fix
Leatrix Latency Fix reduces gaming latency by increasing the frequency of TCP acknowledgements sent to the game server. This also increases the network traffic a little bit.
You can download it from here: http://www.leatrix.com/leatrix-latency-fix