Identify the central atom in BF\_3, which is boron (B).
Determine the number of valence electrons for boron (3 valence electrons) and for each fluorine atom (7 valence electrons each).
Calculate the total number of valence electrons in BF\_3 by adding boron's and fluorines' valence electrons.
Draw the Lewis structure of BF\_3, placing boron in the center and forming single bonds with each of the three fluorine atoms, ensuring all atoms satisfy the octet rule where possible.
Use the VSEPR (Valence Shell Electron Pair Repulsion) theory to predict the molecular geometry: since there are three bonding pairs and no lone pairs on boron, the shape is trigonal planar.