Depends how formal of a work environment you have. At the very least, I would iron out any substantial creases, however, you don’t have to put a vertical crease line in them if you don’t want to (and I think some would just look odd with such a line, depending on the fabric and cut).
As for a proper way to crease chinos, I really can’t say. I would try to follow whatever the original crease was when you bought them as closely as possible. For me, it’s often more trouble than it’s worth to be super exacting about it. If the crease is coming out quickly, then maybe it’s not worth ironing the crease in the first place.