Pond design

I'm planning to build a water garden-cum-fish pond in my garden and am
looking for a simple yet effective design (not the sophisticated koi pond
type) to produce optimum results where pump, waterfall & filtration are
concerned. My pond is going to be about 18ft x 30ft & 1-3ft deep.

I've gone to many websites but I still think getting advice from people who
have constructed and are still maintaining ponds in their gardens would be
the best source of useful feedback.

* I intend to have a skimmer tank which drains to a filter chamber that
houses a submersible pump which in turn raises water to the waterfall tank.

* Can I also drain water from the mid-section or bottom section of the pond
to the filter chamber as well to have more effective filtration?

* Should I also have a separate bottom drainpipe outlet for the purpose of
periodical cleaning of the whole pond ?

What is the best design? What I basically need to know is the most
recommended positions of the skimmer, filter chamber, filter drain pipe &
pump in relation to the position of the waterfall.

I would be most grateful if I could get some useful pointers from you guys
out there .

Many thanks & regards
Danny