The first step might be for you to put yourself in the place of someone who is on the receiving end of your criticism. How would you feel in their place? One reaction, I suspect, would be embarrassment -- particularly if other people were around. But no one likes to be embarrassed, or treated like they're stupid or foolish.
A more serious issue, however, is what an attitude like this says about you. When we constantly criticize others, we're saying by implication that we think we're better than they are. But that kind of prideful, arrogant attitude is wrong in God's eyes, and we need to confess it and seek His forgiveness. The Bible warns that "Pride only breeds quarrels" (Proverbs 13:10).
Don't be afraid to face your own faults, and ask God to help you deal with them. Begin by asking Christ to come into your life. Then ask Him to give you a new love for others. Finally, let the Psalmist's prayer become yours: "Set a guard over my mouth, O Lord; keep watch over the door of my lips" (Psalm 141:3).