For your first questions-DON'T GET TACKY
it's a good idea to stick to a single color of lights (usually white) and continue the rest of your decor along with that same color...but if you're like me, and you have to have multicolored lights, make sure you have other decor to match that decor.
if you have a pathway leading up to your front-door, line the trees up along the path in some sort of patter
you can also get like 2 of those animated grazing deer things, scatter the trees on your front lawn, and put the deer around them.
You might want to take measurements of the places where you plan on putting lights-that way, you know how many you need and you can estimate how many boxes of lights you need to buy.
NEVER USE NAILS TO HANG LIGHTS-it leaves holes and creates a hazard it something goes wrong with the lights..
there are these clips that you can hang from rain gutters, as well as the same clips with an adhesive backing...3M makes some really good ones, but they're a bit pricey..I know that there is this other brand that has a similar product and has a large tub of them for a decent price.
if you need extention cords, make sure the cords are suitable for outdoor use, and figure out how you are going to run them before buying them/setting them up.
Avoid fake snow-it looks like you have a cheap sheet of cotton on your lawn (which is basically what you have), its hard to clean up if it gets wet, and if you have a lot of squirrles in your area, they will chew it up..
a reef is basically a staple in christmas decor-get a reef, but put lights in it (keep it simple and use white lights)
you can buy 2 pointsetta plants and put them outside of your door
For the spotlight-if you plan on doing a nativity scene (idk what your religion is), you can illuminate it with the spotlight..you can also use the spotlight to add general lighting to your decor...aim it downward towards your decor..