On the more static ones I use Rubber Cement as it would be easy to remove and does not do any damage. What works for me (sometimes) on the ones that are less stable is to put a "glob" of Rubber Cement in the spot I want it then wait a few minutes till it gets "sticky" and then put the figure on it. Sometimes works sometimes not. I also use a cement called "School Glue" which seems like regular rubber cement but is more transparent and seems to work a little better. Available at Michael's. Yes I have also used CA when I get desperate
Don