How to drop a table if it exists?

Is it correct to do the following?

IF EXISTS(SELECT *
          FROM   dbo.Scores)
  DROP TABLE dbo.Scores

No. That will drop the table only if it contains any rows (and will raise an error if the table does not exist).

Instead, for a permanent table you can use

IF OBJECT_ID('dbo.Scores', 'U') IS NOT NULL 
  DROP TABLE dbo.Scores; 

Or, for a temporary table you can use

IF OBJECT_ID('tempdb.dbo.#TempTableName', 'U') IS NOT NULL
  DROP TABLE #TempTableName; 

SQL Server 2016+ has a better way, using DROP TABLE IF EXISTS …. See the answer by @Jovan.