In general to dispute a mechanic's lien you need to motion the appropriate court seeking an order directing the party who filed the lien to appear in court and show cause why the lien is proper. The motion must be brought to court in the county where the land is located. In the motion you should explain why you feel the lien is not valid.
Next, the court sets a hearing date following service of the motion.
Then, on the court hearing date, you and the claimant appear before a judge to present your positions. The judge hears the arguments, reviews the evidence you submit, makes a determination as to the lien's validity and enters an order. If the lien is considered improper the judge will order its removal from the records pertaining to your home.
While lien dispute proceedings are not the most complex procedures, you would be well served to hire an attorney to represent you.
I hope this helps.
Note: This observation by the out-of-state lawyer is not proteced by an attorney- client privilege.
In Virginia, the contractor can file memorandum of lien within 90 days of his last day of doing work (or 90 days of the end of the month if the work is ongoing). That is simply filed in land records, and puts the world on notice of the claim. As I stated in my answer to your other question, that can be removed by summary procedure, but only if it is "invalid," not if the issue really turns on how much was owed under the contract. The memorandum is good for 6 months from filing. In order to keep the lien in effect after that, suit must be filed to enforce the lien before the 6 months are up. If they did not file suit, the lien is automatically void.