I have an '01 SE. I want to rotate the tires myself using the
front to back only plan according to the manual. I want to jack up
one whole side at a time. I can use the Nissan jack for one tire
and I have a floor jack for the other. Any ideas where I should
place the floor jack? I'm looking for a safe spot. Thanks.

 

Can you put the floor jack where the tire jack is supposed to go? (shown pages 6-2 and 6-3 of the manual). Maybe use soft scrap wood on the floor jack.

Block the opposite tires front and back, then jack... - AND DON'T CRAWL UNDER THE CAR.

 

Any crossmember is a good place to use as a jack point. Why not just use your floor jack to life the entire side of the car up, instead of using the two jacks?

 

Just place a large piece of wood under the factory jack and it will lift both wheels off the ground.

Otherwise, make a slot in a 8" 2x4 and put it in the factory jack support position while using your floor jack.

Either will work, but I'd trust your floor jack over the factory jack.