This may sound odd but what do residency programs look for? I'm not going to have AMAZING grades...maybe 3.3 or something and I'll pass my boards and I'll be pretty involved with my school but what else are they looking for? This applies to ALL specialities.
If I had to guess I'd say interest in their specialty. Like externships, research in that specific field of dentistry, ect
Many factors-- depends on specialty as well. Don't discount good letters of recommendation/knowing the right people. Class rank is important. Also, some standardized exams (such as GRE or CBSE).
Are you a second year student? If so, much more didactics should be coming your way. My advice would be to hit the ground running this year and try to at least hit top 50%. Research in your field of interest helps, and so do extracurriculars/volunteering-showing your charitable side. Dental students usually apply between 3rd and 4th year if you are hoping to specialize right off the bat, so residency programs really only have the first 3 years to judge you academically. If your school doesnt really start you in clinic till 3rd year, then didactics pretty much carry your gpa/rank. So one really just has to study hard...
LORs means I have to get up close and personal....unless you mean LORs with faculty that I research with? When should I begin doing research in a field I might like? Summer research sounds fun.
Summer after your first year of dental school. This is also a good chance to get a rec letter. I believe the NIH also has summer research programs for professional students, and also offers year-long research opportunities to which you could avail yourself in the middle of dental school (I think, so long as your school permits a leave for a year). Depending on your program and your aptitude, you might also have time third or fourth year for research.
Any research is better than no research, so pick something that interests you. Lots of research could relate to any field. Also remember that this is for a brief period of time, so it's not that important. Just pick something/an advisor that will probably result in you getting a publication.