How did southern states prohibit African Americans from voting after reconstruction ended?

Even after the 15th Amendment white southerners mostly kept blacks away from the polls by intimidation. Also many clauses were added to keep blacks from voting such as the one that required them to be literate (the ability to read and write) to cast their ballot. There was also something a Poll Tax (a tax which was imposed on someone when they went to vote) which was only imposed upon the Africa Americans.