Newbie plumbing advice

[trilinearmipmap]

Hello I am one of those people who have lurked on these boards without ever actually setting up a reef tank.

I have questions about what to use for plumbing. Most peoples tanks I have seen pictures of use rigid PVC plumbing with harsh 90 degree angle bends in it. I understand that rigid plumbing with sudden 90 degree angles cuts down on your flow. Should I use flexible tubing instead? Also do they make PVC in slow U-shaped curves (better for flow) instead of harsh 90 degree angles?

I will be plumbing an Oceanic 58g reef-ready tank and I will need to plumb from the standpipe down to my DIY sump, also I will have to plumb my return pump (3/4 inch threaded) up to the return pipe. Any tips or links to good advice on plumbing a tank?