The body said it had published Ethics and Professional Standards in a bid to provide more clarity and support to members.
Among a range of issues, the document covers professional competency; gifts and hospitality; and use of social media.
It also includes a nine-step checklist for making ethical decisions.
On potential conflicts of interest, the document said: "Identifying a conflict does not necessarily mean you have to stop work, but it does mean that you need to take reasonable steps to ensure that it does not affect your decision.
"This might mean declining or standing down from a commission, or requesting that someone else deals with a case, or in some circumstances having clearly laid out internal safeguards in instances where members within the same organisation are advising on different sides of a planning matter."
The document also says that social media, such as Twitter, Facebook, LinkedIn and Instagram "is increasingly a feature of professional activities and personal lives.
"Where there is overlap, you should consider making a distinction between personal and professional viewpoints, for example by adding a disclaimer to make it clear that the opinions expressed are your own and not the views of your employer".
RTPI head of careers, education and professional development Andrew Close said: "This guidance addresses a wide range of different situations and should help members steer through them with more confidence and exemplify the professional behaviour expected of them."