When seating bearings (be it on a trailer, truck, whatever) I like to spin the wheel as I tighten the nut with the socket. I will generally go pretty damn tight and in both directions. This is to seat the bearings. After that I will spin it all the way back off to the point that I can spin it with my hand. I then run them down hand tight holding just the socket. You don't want any play, but tapered roller bearings, especially once they're used, really don't require much in the way of preload. Again, I said HAND TIGHT. If, and only if, my socket is extremely greasy and the threads on the spindle are a bit tight I will go perhaps a 1/4 turn beyond with a ratchet. The one exception to the rules would be my wheeling rig which requires a bit more preload (say 3/8 turn with the ratchet) on the bearings to support the giant tires and keep the bearing creep to a minimum on the spindles. Of course this also means I'm buying new thrust washers and lock plates once a year.
Again, that's hand tight. In the case of something like a trailer where there is no double nut setup and you just have a cotter pin through a castelated nut it is better to back it off than move it tighter to get the hole to line up unless you just need to nudge it.
Trailer bearings are big business for all of us in the shop given our prime location on the main gateway to the northern Minnesota lakes.
*edit* You did pack the bearings well (assuming you don't have oil bath hubs), right? I prefer to pack my bearings by hand as long as I'm not trying to beat the clock as the packing machines tend to either leave large voids and air pockets or waste a TON of grease getting them out. Also, it's tempting to pack the void between the bearings with grease, but this is NOT a good idea. It will not magically work its way into the bearings to lube them if the seal fails and slings grease and it will retain heat. Bearing Buddies make guys like me a ton of money because of that very reason.