Good post by many. Three times profile works a treat. The classics(bless em) fly a much better "Path" than the NG's do(if left in LNAV/VNAV). Having said that if you are going to leave it in LNAV/VNAV then have a look on the descent page and the most limiting height/speed will be highlighted, look below the highlight and it will display the required rate of descent to achieve the required height and speed. If this rate of descent is not being achieved then do something about. This may be LVL CHNG,V/S or even the addition of thrust to a steeper than desired path.
But most of all ask lots of questions, most pilots really appreciate someone who is willing to ask and learn.
Oh, and don't forget the 737 is a tractor and deserves to be driven as such(oh how i miss the F-100!!).
But most of all..................enjoy!