There are many ways to perform drop the existing objects before create them. One of the common way use OBJECT_ID as shown below.
--for a permanent table you can use
IF OBJECT_ID('dbo.tabl1', 'U') IS NOT NULL
DROP TABLE dbo.tabl1;
--for a temporary table you can use
IF OBJECT_ID('tempdb.dbo.#tbl1', 'U') IS NOT NULL
DROP TABLE #tbl1;
In SQL Server 2016, new function DROP IF EXISTS introduced to perform this task. Currently, the following objects can DIE.
DROP PROCEDURE IF EXISTS
dbo.tabl1, dbo.tab2, dbo.tab3, dbo.tab4, dbo.tab5, #tbl1;
--to drop Stored Procedure
DROP PROCEDURE IF EXISTS
dbo.sp1, dbo.sp2;
Cheers!
Uma