Hi Regis,
Sometimes, you will see the letters p i m a above the notes in tablature; this is an indication that the song should be fingerpicked.
Here is an example of that in action.
Fingerpicking is rarely used with electric guitars, so that is another thing to consider as well. Chances are if you're not sure, it's probably played using a pick.
Just my two cents of course. Hope it helps.
