When giving constructive criticism, you probably don't want to come off as a jerk. A better way to offer criticism may be this four-step strategy formulated by social psychologist and game theorist Anatol Rapoport.
Brain Pickings excerpted the "rules" or steps below from a book by philosopher Daniel C. Dennett. They're meant to foster better discussion between you and the person you're criticising, not just soften your criticism. These are the steps:
How to compose a successful critical commentary:
1. You should attempt to re-express your target's position so clearly, vividly, and fairly that your target says, "Thanks, I wish I'd thought of putting it that way.
2. You should list any points of agreement (especially if they are not matters of general or widespread agreement).
3. You should mention anything you have learned from your target.
4. Only then are you permitted to say so much as a word of rebuttal or criticism.
This is like the "sandwich" approach to delivering criticism, except instead of compliments, you tell the person what you agree on and how the person has enlightened or informed you (if they have, that is). It might come off as more sincere than just complimenting the person before offering criticism.