Database Designing help

i have good knowlegde about DBMS. but I have never done any designing professionally. i am a student.
Question 1. can someone guide me how to do that. i mean Steps.

i am trying to increase my skills. so my current problem is

i have table
1) Subject with (subject_id)
2) Student with (Student_id)

Question 2) i want to make a new table MARKS

how to do that so my database stay normalise.

Student_id,Subject_id,Marks
will it be okay to have many similar entries in student_id with diferent subject_id and different marks?

OR
do i need 1 more table.

thank you.

after designing it in conceptual,logical and physical levels.

question 3) what are the steps to normalize my database. i know about all normalization forms. but how to achieve them?