Heavy dice (metal) seems to help--at least for me. I also find the d6 very hard to spin. I'll have to run some tests during Friday night's game, because I can't remember which oneis easier to get spinning. I do recall that the d6 seems to spin longer than the d4.
Of all the useless talents to have, I appear to be able to spin dice very well. The d4 is probably the hardest though. I can even spin a Crystal Caste d4 or d6 more easily than a regular d4.
Many-sided dice are easier to spin because they're more spherical shaped. The exception is d8 (because of the bogus shape of it), but I imagine it is still easier than d4. A sphere being infinite sided is the easiest to spin!
I always thought d12 spun the best or at least was the most fun to spin.
Not only can I spin them, I can stack them. (Old school ones, anyway; some of you doubtless know what I mean and have done it yourselves: the tower of dice that begins with an upside-down d4 and another d4 atop it, then moves upwards...)