Assuming you're using 35mm and stainless steel reels, treat yourself to a couple of Hewes reels. Instead of the center clip, the Hewes reels have edge cleats that grab the sprocket holes, making it far easier to maintain a consistent light tension on the film while loading.

I believe that most 35mm loading errors on stainless reels occur toward the beginning of the roll, where a loose (or, off center) clip makes it difficult to keep the film from moving in and out, causing it to jump the spirals. Too much curvature can also cause that problem. My technique is to hold the film in my right hand, spool between my little finger and the butt of the palm, feeding the film out between the thumb and index finger. By placing the thumb and index finger on the edge of the reel, and allowing the friction to maintain tension, that works for both aspects (tension and curvature). I rotate the reel with my left hand, being careful to keep the motion steady.