As a casual driver, I still like to drive swiftly from light to light. I have never raced with manual myself but what I have learned from driving my Z is shifting when it feels right with the car. Now I am not sure if my shifting is where it should be exactly but I know the owner's manual seems low like previously stated by other Z owners. This is how I observed my shifting:

1st to 2nd @ 19 mph/3.5k RPMs
2nd to 3rd @ 39 mph/4-4.5k RPMs
3rd to 4th @ 58 mph/4-4.5k RPMs
4th to 5th @ 75 mph/4-4.5k RPMs
5th to 6th @ 90 mph/4-4.5k RPMs

Basically I shift at 3500 rpms to 2nd and between 4000-4500 for the rest. Seeing this is my first manual sports car, if anyone has any recommendations for adjustments feel free to let me know. Thanks.

 

Guys 2.5k is not lugging the engine. Lugging the engine is bringing it below idle speed (~1-1.2k). Shifting at 2.5k is perfectly fine as long as you're above 1k in the next gear. It'll save gas and place less wear and tear on your motor. 3k or 1/2 redline are great as well but they suck up more gas.
NzZ

 

I'd have to agree that 2.5K is not lugging at all. I shift at that RPM when a cop is following me so I won't be as noticable.

I like to drive in the 3 to 4K range as that is close to the start of the real power. That way if I have to make an emergency manuver or I just want to jump on it, all it takes is a little more throttle and away we go!!!!!

In AutoX, I usually shift in the 5-6K range. That seems to be the point where it doesn't seem to be pulling quite as strong. Then again, maybe it's because that's where I'm coming up on a curve and need to slow a little.

 

Exactly Dave, I like driving in the 3-4k range too. Just before you really tap into the power. At 4k, the engine is just starting to 'percolate' as I describe it. Anything over that is just sweet! I'm not driving the Z to conserve gas. These babies are for fun, right?

 

I usually stay in 1st till 4k and then shift.

Now if I am racing, I keep it till it just hits redline and then shift.

 

ditto look at chevy f-body's and corvettes they all have skip shift which forces you to shift from 1st to 4th unless the engine isn't up to temp, or you are over 3.5K in 1st ... short shifting and skip shifting is perfectly fine and will save you gas unless you skip shift and then floor it trying to accelerate while in the wrong gear for quick acceleration... Normal driving I will shift around 3k in first ditto for 2nd maybe a little less then go to 4th.