how long should i charge my d400 battery for the 1st time?

Just charge it until the light turns green on the charger, but I don't think you're supposed to leave it in there longer than necessary.

Unless the charger is radically different from other Canon chargers, it should turn green when it's ready... you can leave it in the charger for an extra few hours if you want, but I doubt it makes any real difference. The battery technology on SLRs isn't really particularly different from P&S camera batteries.

My only advice is that, if you are coming from P&S to dSLR (as opposed to film SLR -> dSLR), then read the manual, and start learning how to work the controls. Invest time in understanding what happens when you change the shuttering speed, what happens when you aperture down, how to control the light meter, how to manually focus, etc, etc.

A related piece of advice is that if you are using a zoom lens, a good exercise is to fix it at a single zoom, and then experiment with only taking pictures at that zoom, moving your body around instead. One of the biggest mistakes people who use P&S cameras make is that these two things are equivalent -- they're not.

Anyway, congratulations, and make sure to post pictures here!

To quote Canon...

After the lamp lights, continue to recharge the battery for 1 hour to attain a full charge.

Have a look in your handbook .....

Hi student_trap,

what camera did you have before the D400? I should be getting one very soon and I'm hoping its good. I just wondered where you were coming from Camera-wise.

Cool, can't wait!