Step 1: Use lewis structure guidelines to draw the lewis structure of BCl₃.

Step2: Apply VSEPR notation, A X E
A=Number of central atoms
X=Number of surrounding atoms
E= Number of lone pairs on central atom

For the above molecule VSEPR notation will be AX₃E₀

Step 3: Use VSEPR table to find the shape. AX₃ has trigonal planar shape. So the shape of BCl₃ molecule is trigonal planar.
Download a copy of VSEPR shapes table here

Bond angle in BCl₃

Bond angle of Cl-B-Cl covalent bond in BCl₃ molecule is 120º.The representation is shown below.

Image courtesy:wikipedia.org