When making a Lewis Structure, you don't initially know how many bonds there will end up being. So start by counting up all of the valence electrons each atom in the molecule has. This is how many electrons there need to be in the Lewis structure.
Then use a single bond to connect them to each other, and then give each atom an appropriate number of lone pairs. Now
count up all of the electrons in your Lewis Structure. If this number is greater than the valence electron number you started with, you know you will have to add bonds, until the number of electrons in your structure matches the number of valence electrons you initially calculated. Keep in mind, each bond line signifies two electrons.
This video example may be helpful: https://www.youtube.com/watch?v=xDG8EQ2Fq8w