hahaha - yeah, there's still a few out there
How to specialize?
Step 1 - Figure out what you want to specialize in! Remember, specializing means limiting yourself - you are excluded from practicing outside the scope of your specialty while you practice as a specialist. A popular alternative is to set up your general practice with an emphasis on certain aspects of dentistry you like, and refer out the rest! Don't like dentures? Send them to me.
Step 2 - Spend a lot of time with residents/faculty in the area of specialization you're considering. This is usually done concurrently with Step 1 as you're figuring out what you want to do, but I can't emphasize the importance of this step enough. You'll learn a lot about the specialty you're considering just by spending time with those who are in it.
Step 3 - Get some exposure outside of your school. It's amazing how uni-dimentional a dental school can be. Escape the chains and see what other people are doing in that field! Shadow at a private practice or visit another school. For some specialties this is pretty much mandatory so they know that you know what you're getting into.
Step 4 - Apply. Each specialty does this differently and you'll need to get past Step 1 to delve into the specifics here, but by the end of 3rd year you should have a solid amount of stuff you can put onto an application. Good grades, experience, letters of recommendation, research, extracurriculars, etc. You've done this before when you applied to college and dental school - this time isn't any different.
Step 5 - Enjoy long hours, tons of reading, and complete immersion in your field of choice. Hope you're passionate. They call it a residency for a reason - you live, eat, breathe it.