How do keep a garter-belt and stockings or pantyhose from sliding down your waist and legs?
If you buy the correct sizes, you should not have a problem.
The garter belt should be large enough to fit around your waist, but small enough so that it does not slip down over your hips. You can adjust the size of the belt to accommodate your waist and hip combination, but do not make it too tight and create an unsightly bulge.
The stockings should be long enough so that their tops reach the clasps of the garter belt. You can adjust the length of the garters so that the clasps meet the top of your stockings. If the stockings are too short and need to be stretched to their outer limits in order to reach the clasps, you are likely to experience slippage as you move about.
You did not ask, but be sure to attach the stockings to your garter belt before putting on your panties.
Size matters with pantyhose, too. The only time I had problems with pantyhose is wearing a pair too small for me. The pantyhose must be large enough so that their waistband sits at your waist and is tight enough so that it does not slip down below your waist, but not so tight that it creates a bulge.
Like stockings, if you have to stretch the pantyhose to their outer limits in order to get them to fit properly, then the pantyhose are too small and they will slip down your legs as you move around.
Do you need advice concerning femulation or other crossdressing-related matters, then e-mail me and I will happily give you my opinion on the matter. My e-mail address is stana-stana at sbcglobal.net.