Do not flaunt your wealth (jewellery and other expensive looking personal belongings and cash). They even love to craft funny anecdotes about socio-economic-political situations and adversaries in life.
Avoid wearing immodest or revealing clothing, especially in Muslim-dominated areas where there is a clear standard for appropriate attire. But it is not appropriate for a foreigner to comment on the political situation nor discuss about religion.
With regard to socio-cultural conflicts and issues, just listen during discussions and do not take sides.
Good discussion topics include: family (Filipinos love to talk about their families), where you are from (bring pictures of Canada with you, post cards may do) and the reason why you are in the Philippines (explain explicitly and clearly your organization’s aims).
Most Filipinos do not mind being asked their age, so it would not be unusual for them to ask yours.