Slowing down: Take a deep breath, Calm yourself down before you start speaking. If you dive into speech without taking time to ground yourself, you may speak more quickly and slur your words.
Articulate your words: Pronounce each syllable individually. Syll - a - ble. Gradually speed up your speech and decrease the space between words until you are speaking normally. Practice when you're alone.
Speak with Inflection: Think before you speak, Questions should ascend in pitch at the end. Statements should inflect somewhat deeper, with finality. Suppose you're reading a story to a small child.
Practice & Be Confident: Don't be afraid to speak loudly and clearly. Practice saying tongue twisters and try practicing in front of a mirror or just make one snap and then see how you're conveying and learn from it.
Grammar & Vocabulary: Avoid speaking in run-on sentences. If you let yourself ramble, your listeners might miss the point. Expand your vocab, Reading is a great way to expand vocabulary.