Looking for a Trigger to change inserting strings?
if you want to use triggers thats your call, i am just suggesting a different approach

you can use the Default Value or Binding feature of a table

e.g in your table1, you can make the default value of Name column = 'Sample Name' by below script

ALTER TABLE table1 ADD CONSTRAINT
    DF_Table1_Name DEFAULT N'Sample Name' FOR Name
GO


Look at image below




This code below adds a trigger to your table that works after insert, it updates the name added and replaces the 'x' with '*'

CREATE TRIGGER ReplacingTrigger 
ON  table1  
AFTER INSERT 
AS  
BEGIN 
    UPDATE table1
    SET table1.name = replace(table1.name,'x','*')
    FROM table1
    INNER JOIN inserted i on i.name = table1.name
END 


i suggest if you have an ID in the table to use it in the joins to find the exact record inserted to make it accurate like below

CREATE TRIGGER ReplacingTrigger 
ON  table1  
AFTER INSERT 
AS  
BEGIN 
    UPDATE table1
    SET table1.name = replace(table1.name,'x','*')
    FROM table1
    INNER JOIN inserted i on i.id= table1.id
END