Top off charge out of the box?

I always plug mine in and charge to 100 then use it like normal. One time isn't gonna hurt anything. I usually charge to 100 before powering the phone on.
 
Li-ion batteries are supposed to be broken in already from the manufacturer, so I would just use as normal out of the box.
 
I usually try to charge it to 100 or close to it before getting it started and all that. Mine will either show up tomorrow or the next day
 
Or should I drain the battery then do full charge?

Avoid regular deep discharges of a lithium battery -- if you do it fairly regularly, it will decrease the overall lifespan of the battery. As mentioned before, just use it. But keep in mind, setting up a new phone often uses up a lot of power, since you're doing a lot of app installations and updates, so keep an eye on the level.
 
I stopped caring awhile ago but out of habit I use it up out of the box customizing, setting her up letting it go down less than 10%, then fully charge her.