I guess the answer is..."It depends". On the weather, for starters, or what the occasion might be.
Generally,since I really like the feel and look of top shelf, quality sheer hosiery, I'll wear pantyhose or tights over a pair of silky bikini panties. If it's a little on the warmer side, then I'll ditch the pantyhose and either go bare legged or "cheat" by wearing a pair of thigh hi nylon stockings. If the occasion is a little more formal and less risque, then it's hose and panties.Same for at work in the office. If the weather is on the colder side, and woll fabric starts making an appearance, then a slip may come into play, to prevent scratchiness. If I'm dressing for an evening and just looking to shake my tail feathers then It's garters and nylons, and who cares who sees what! That may be the objective!
Underwear? Lol. Which kind depends on my mood, what happens to be clean, and how much coverage and/or flowiness the skirt or dress has. Generally, the shorter the skirt, the more coverage I like my undies to give, because I like to dress how I want, but I'm not into showing off 'the goods' or making it too easy for things to accidentally get exposed. They're still pretty undies though. I figure if there's a chance they may accidentally be seen, better that I have something nice on that I like, but still covers to my preference. Sometimes I'll wear tights too, especially once the weather starts getting colder.