Making sure steering wheel is straight before alignment

[Zenwren]

My steering wheel has always been off centered going down the road, the truck has also had a couple different aftermarket wheels before I got it so I know the thing is just stuck on there in a random position. I just finished rebuilding the whole front end and it's time for an alignment. What should I do to properly center it to the steering gear before taking it in? Do I just count the turns from one lock to the other and spin it back half as many turns before putting the steering wheel on straight?