Exotic hardwood installation preparation

I’m installing 3/4″ hardwood flooring as part of a renovation. I’m rather new at flooring installation, and have two questions.
Firstly, the floors in this 50-odd year house are not flat; they have high and low spots, about 3/16″ over about 3-4 feet. What is the best way to flatten the floor to accept the hardwood? I’ve heard specs of 1/8″ over 10′, but no suggestions as how to achieve this.
Second, the area to be covered includes the original house, plus a previously-built extension area. The joists in the extension run perpendicularly to those in the original house. Can I run the wood flooring straight through (from front to back of the house) or do I need to stop it, and change direction for the extended area?
Replies
Check out hardwoodinstaller.com for a good floor forum.
You can sand down the high spots a little, if they are localized. You can shim the low spots with pieces of 30# felt paper. If the floor is bad enough, you might consider removing the decking and doing some work to the floor joists.
If you use a good underlayment, like 3/4" advantech or plytanium, you can usually run the boards in either direction.
"When asked if you can do something, tell'em "Why certainly I can", then get busy and find a way to do it." T. Roosevelt
Thanks!
I've checked out the hardwoodfloorinstaller site, and it does have some good info there.The subfloor on the extension part is 3/4" ply, plus 1/4" poplar underlay.
Hopefully, that will be good enough.