After you have purchased the tax lien lists you wanted and researched the properties you want to acquire the tax lien certificates on, the last step is to contact the county treasurer's office to double check that the tax lien certificates you want are still available.
When you speak with the treasurer's department on the phone, inform them that you will be acquiring the certificates through the mail and they will tell you the correct procedure to do so. Each county's procedures are slightly different, but they are all very helpful in ensuring you get the certificates you want.