I am building a bike at the moment and I have just received the forks. I wnat to know get the headset , stem and handlebars.

The forks are Surly Ogre and the frame is an old aluminium hybrid trekking frame. I am probably going for the Velo Orange Casy's Craxy Bars for versatility. The headset will probably be the Cane Creak 40.

Now how do I go about making sure I get a correct stem with angle and length ?

Any hints on what I need to be doing ?

If you have a previous flat bar build sitting around that fits you fine (and you want the same position), then you could do the figures once you have the fork and headset and installed on the frame:-

Using the old bike (positioned so the dropouts are in a horizontal plane to the ground), measure the stack and reach to the stem/handlebar centreline, using the BB centre as your anchor point. Make a right-angle mock-up and set it against the new bike. You should be able to get an approximate stem length required. Use an angle tool for the degree (taking into account spacers required and stem stack-height).

IDK about you, but myself , when the fit feels good , I can look straight down thru the axis centerline of the steerer tube, while riding .