I love to wear a garter/suspender belt with sheer stockings. Contrary to popular belief they are really comfortable, but with the odd strap tug to keep you aware of your sexy underwear!
I find that for all day comfort you need to wear a really deep elasticated belt (4 or more bra clasps deep), so that it fits a bit like a corset. It's a bit like wearing a bra: when you first put one on it feels tight, but you come to appreciate the snug support of a firm garment with deep side panels.
You should look for belts with 3 or more straps per side, and with metal clasps. More flimsy belts are for the bedroom only, not for all day wear.
The rear suspenders should be attached first. Swing your belt to the front a bit, likewise your stocking top. Fasten the clasp then swing both to the rear. Repeat for the other leg. The idea is to get your rear suspenders sitting tight over your bum!
I find that stockings with plain tops are easier to attach than those with pretty lacy tops. I wear a garter belt with sheer nude stockings, barely black stockings and fishnets, but I have never tried seamed stockings as it might be difficult to get the seams straight.