Great thread. When I first started out, I stacked the few records I had horizontally and while not all of them have warps, there are a few that did develop warps and I can't play them anymore; thank goodness they weren't expensive audiophile releases.
For storing vinyl, I have a home made cabinet which I've put felt lining around the inside of so pulling records and boxes out is smooth on the bottom. For actual storage, I generally reuse shipping boxes to store the records inside (photos attached). I think @April Snow was referring to the same type of thing in a post above. I ran out of cabinet space and I'm now lining boxes up on the floor. Most of the small-width boxes are pretty good, but I have two larger boxes filled with MOFI records; the records tend to show a bit more left-right lean that the ones in the smaller boxes. I've also started keeping the inner marketing sheets that MOFI ships and keeping them around the record when I stick it back into the sleeve (I've discarded quite a few over the years until I decided to start keeping them).