I feel it is important to do the following before attempting the song.
1-Study the chord progression. Is it familiar?
2-What key is it written in, and are there any key changes.
3-What is the mood/feeling of the song.
4-What is the tempo of the song?
5-Match a style to fit the feeling.

This really does not take too long -- and you may learn something you can use when learning your next song.

Now how many times do I play the song?
As many times as it takes to make the song sound reasonably good.

John C.