Gingivitis
In general, symptoms progress over time and include:

Pain is usually not a symptom, which partly explains why the disease may become advanced before treatment is sought and why some patients avoid treatment even after periodontitis is diagnosed.
Amaliya , Timmerman MF, Abbas F, Loos BG, Van der Weijden GA, Van Winkelhoff AJ, et al. Java project on periodontal diseases: the relationship between vitamin C and the severity of periodontitis. J Clin Periodontol. 2007 Apr;34(4):299-304.
de Oliveira RR, Schwartz-Filho HO, Novaes AB Jr, Taba M Jr. Antimicrobial photodynamic therapy in the non-surgical treatment of aggressive periodontitis: a preliminary randomized controlled clinical study. J Periodontol. 2007 Jun;78(6):965-73.
Kolahi J, Soolari A. Rinsing with chlorhexidine gluconate solution after brushing and flossing teeth: a systematic review of effectiveness. Quintessence Int. 2006 Sep;37(8):605-12.
Persson GR, Yeates J, Persson RE, Hirschi-Imfeld R, Weibel M, Kiyak HA. The impact of a low-frequency chlorhexidine rinsing schedule on the subgingival microbiota (the TEETH clinical trial). J Periodontol. 2007 Sep;78(9):1751-8.
Staudte H, Sigusch BW, Glockmann E. Grapefruit consumption improves vitamin C status in periodontitis patients. Br Dent J. 2005 Aug 27;199(4):213-7, discussion 210.