I'm going to radially lace my wheel as soon as the spokes get to my place tommrow, but I'm not sure if I should have all the spoke heads facing inwards, outwards, or should I alternate them. Any suggestions?

Do whatever you think looks best. Functionally it will all be the same.

Head-in gives you a better bracing angle and theoretically improves wheel strength/stiffness. Head-out reduces stress on the hub flange. Does it really matter either way? Probably not.

Heads out looks way freaking better, IMO

Head in should theoretically give you a wheel that's a little more stiff laterally, and a little more "compliant" vertically, with the reverse being true for head out.

i like alternating in/out.

Why? They don't need to be interlaced.

Head out - It's much better for the spokes. Since they're under more tension, this is something you should care about. If you look at it, lacing them head in causes more stress on the elbow 'cause it has to bend just a tiny bit further in, and over the lip of the flange. Head out gives you much more of a straight shot to the nipple.

I don't build wheels, so I really don't know, but I always thought that where the spoke crosses the flange actually relieves stress on the spoke elbow in the case of the wheel being built "head in"

when it comes to radial, every cracked flange I've seen is from spoke digging into the flange. I'd lace it head out.