Some clichés that may be familiar: "from the bottom of my heart," "to the depths of my soul" - these stock phrases take no imagination, and do nothing for your poems.
The reason that most amateur poets use clichés (other than laziness) is usually an attempt to side-step sentiment and go straight for the easy road to sounding "poetic."
But I saw that phrase in a poem by SHAKESPEARE! Yes, and when Shakespeare used it, it was new, fresh - it was his own invention. As James Joyce wrote: "After God, Shakespeare has created most."
A friend of mine, and one of the finest poets writing today, said that one of the reasons she was excited by writing poetry was the possibility of changing the world for someone - of coming up with an image that was so new and inventive that it changed their perception of that thing forever (although she said it far more eloquently than that).
So don't believe the hype. Avoid cliché as if it were a social disease.
I said "Sentiment," not "Sentimentality"
What's the difference? "Sentiment" is simply a thought or feeling based on feeling rather than reason. "Sentimentality" is an idea or expression marked by excessive sentiment. The former will give your poetry "depth" without pandering - the latter pushes the line by trying to artificially make a sentiment do more work than it can handle. It's the difference between comedy and farce - between drama and melodrama.