noun
Usually carries a negative connotation, implying a cunning, underhanded, or questionable way of doing something.
彼のやり口はいつもずるい。
His way of doing things is always sneaky.
詐欺師のやり口に引っかからないでください。
Don't fall for a scammer's tricks.
やり方 is a neutral term for 'way of doing' or 'method', while やり口 often implies a negative or cunning approach.
Compound of やり (continuative form of やる 'to do') + 口 (くち 'mouth; way'). The negative nuance likely developed from the idea of a 'mouth' or 'opening' used in a cunning manner.