Site redesign affecting positioning

[Raymond]

I have received a job to completely redesign a website (backend and frontend). One of the most important requirement of the job is to maintain its current position on search engine for the targetted keywords.

Changing a website inside-out like this will definitely affect many important factors that calculates SERP. Keyword density will be different, some old links will be invalid, basically, every single item will be different.

Do you have any procedures to follow so that the impact on such change will be minimized?

[netscan]

Re-directs will be important for the invalid links that are currently being spidered.