Any tips and tricks on how to make cake squares so that they look neat and clean? I have to make about 150 :)

Practice. Patience. Practice some more.

150 miniature square cakes??

AI bet by the end of the 150 you'll be very good at them :D

What size? Do you mean petit fours?

• Use a long, straight-edged, sharp knife.
• Wipe down blade between cuts.
• Trim all edges before cutting pieces.
• Use a ruler or tape measure for equal-sized pieces.

No way man, I'd buy a Squires pan, those pans that bake individual squares. That way they keep the tight crust on the edges.

The OP needs 150 cake squares. Icing a sheet cake then cutting into squares is less labor than baking little individual cakes and icing each damn one. In my very humble opinion.