Yep, straight as possible, slow and gentle pulls, and try to keep the cardboard edges of the reel from getting too battered about so that they get bent out of shape (yes, sometimes hard to avoid in the field, I know!).
An assistant works wonders too, but I won't let the GC I work with reguarly help in this respect anymore. He just lays the reel flat and pulls the cable upwards, leaving a nice long spiral of kinks! Grrrrr!