There are various options for tempo changes, some are more common than others. Tempo changes are often easy to perform if you already can play the song, as it is about playing slower or faster (ritardando/accelerando), playing without musical pulse and doing musical stops (rubato/fermata) or change the feeling of the pulse and thus the pattern of the song (half time/common time). In Chords On Piano 1-3 you can see more instructions on mechanisms related to the music's tempo, which is related to specific songs.