I'm sure someone will write an article, but here's a shortlist to tide you over:
- Normal forms (I would recommend knowing up to 4NF at least): Why is it important? What does it mean? How do you implement it?
- Standard ANSI SQL keywords and usage (I would recommend at least to ANSI SQL-89 as a bare minimum)
- The difference between DDL and DML
- The differences between Clustered and Nonclustered Indexes: When should you use each? What are the advantages/disadvantages of one over the other?
- Primary Keys, Candidate Keys, Surrogate Keys, Foreign Keys: What are they? Why are they important? When do you use them?
- Unique Constraints, Foreign Key Constraints, and even Check Constraints: Again, what are they and how do you use them?
- Data Types: the basics - INTEGER, CHAR, VARCHAR, NCHAR, NVARCHAR, NUMERIC, etc. When would you use each type? How do you define a column as a specific type? How are the types like CHAR and VARCHAR different from one another?
- NULL: What is it and how do you use it?
This list covers enough of the basics to design a decent database. Once you have played with these, and know them well, you should get experience with advanced (and SQL Server-specific) topics, like Stored Procedures, UDFs, XP's, Query Execution Plans, Filegroups, Server Configuration, how to use Profiler, etc.
The key is not to just memorize the definition of - as an example - "First Normal Form", but to actually *know* what 1NF means, why it's important, and how to achieve it. That kind of knowledge (for me anyway) comes from actual experience as opposed to memorization or certification exams.