Drag and drop will only be useful if you know how to design the database schema in the first place. And if you can do that, issuing a create table in any dbms is a breeze anyway, so a drag and drop solution would become more or less irrelevant. Since you are asking the question, I'll assume you don't have previous design experience.
This is not something that can be explained in a single post. I did find a crash course online article though, that with a quick scan over looks like it covers the basics including why normalization is important. You can see that here: http://www.informit.com/articles/art...02167&seqNum=2
You can search for additional with a simple query of "database design principles". Storage design is the single most important step during the design phase. If it don't work on paper it won't work in practice. Proper design is the difference between impossible/horrendously difficult queries, and easily managed queries.