The guidelines form the first best practice code to have the full backing of the major advertising bodies - the IPA, ISBA and the Direct Marketing Association - as well as the Marketing Communications Consultants Association and the Public Relations Consultants Association.
The growing role of the "marriage brokers between agencies and clients has also been acknowledged in the guidelines, which have been endorsed by intermediaries such as the AAR.
The code is a development of the pitch guidelines agreed between the IPA, ISBA and the DMA in the late 90s and takes into account the significant changes which have taken place in the agency selection process since that time.
Among them has been a decline in the number of big pitches in favour of workshops, chemistry sessions and trial projects and the growing influence of client procurement specialists in determining agency appointments.
Debbie Morrison, ISBA's membership services director, said: "Managing successful relationships with communications agencies is complex. With the tone of the relationship often set early on - even before the formal appointment of an agency - the review and pitch process is crucial if the partnership is to develop successfully and produce high quality results."
The guidelines urge clients to think deeply about whether they need to call a pitch and whether an existing troubled agency relationship can be repaired. "There's evidence of too much churn of accounts which isn't in the interests of brands or shareholders, Hamish Pringle, the IPA's director-general, said.
Clients are also asked to consider the strain on their own resources and those of agencies caused by a pitch, to avoid the "scattergun approach to agency selection.
Copyright and remuneration questions should be resolved at an early stage as well as the PR fallout. "Clients should be open with agencies about what's going on, Pringle added. "They should not have to learn through a press leak that their major account is up for review."