1. If you're in a gui you can run tracker-preferences and disable the indexing of all folders.
2. To delete existing tracker logs you need to do
tracker-control -r
This kills all running tracker processes and removes the databases.
3. Finally, edit /etc/xdg/autostart/tracker-miner-fs.desktop and tracker-store.desktop and change
X-GNOME-Autostart-enabled=true
to
X-GNOME-Autostart-enabled=false