You need to file a lawsuit - such as in small claims court - for monies owed. You need to serve a copy of the court papers on the other party. At the time of the court appearance the judge will render a decision. If it is in your favor, judgment will be entered against the other party. Once you have a judgment, you can file an Abstract of Judgment, have it recorded. It may not be necessary to place a lien on their belongings that you are storing - is it of value? It would be better to seek out real estate owned for lien purposes.
Another suggestion would be to seek a Writ of Possession - to gain ownership of the belongings when filing. But, that's up to you.
Further, concerning the belongings, as evidence for your case, gather up all receipts, paperwork to attach as exhibits when filing suit.
You should also send a letter to this person (certified mail, return receipt requested), advising them that you wish for them to claim their property within 15 days from the date of letter and to reimburse you for storage (be prepared to submit the total amount owed, including copies of any and all receipts), otherwise, you will be forced to take legal action against them by seeking a Writ of Possession and complaint for monies owed. Keep a copy for your files. Your return receipt and copy of letter will be part of the exhibits.
If you wish for further information, please let me know.
Peace, Love & Happiness,
The Mystic Wave