I decided that I definitely wanted to pursue dentistry almost 3 years after finishing undergrad. I don't like taking risks (such as quitting my job to take prereqs in one year), so I decided to take the prereqs at night while working full time. Due to limited availability of night classes where I live, I'm still 8 hours short on the prereqs and it's taken me 2 years to get to the point where I am applying.
If someone could have given me advice from the start I wish they would have told me the following things:
1. Take Chemistry I & II, BIO I & II, and O-Chem I & II before taking Physics I & II or the 3rd and 4th required biologies. Those last 16 hours are required by most schools but aren't needed to help you on the DAT. If you get accepted in December of the year you apply, you can always finish those last 16 hours between December and matriculation.
Interesting thread... any other non-trads out there...
2. Shadow early to know that you're sure about this and also to get started on working towards a letter of recommendation from a dentist. I actually could have applied last year because I could have finished my prereqs up this summer, but I did not have any connections with dentists and most schools require a letter from a dentist.
3. Take each class with the thought that you might ask that professor for a letter of recommendation. Answer questions in class, talk to the professor, and let them know that you plan on applying to professional school.
4. You don't need all of your prereqs done to apply. Looking back on things, I seriously wish that I would have applied last year. I'd be one more year closer to being a dentist, and it also would have been a better financial move since I'll make more in that one extra year as a dentist than I would in this one extra year in my current career.