thrifted dress (this works with any button up dress but this Zimmerman dress would look cute, a plaid one from BB Dakota here, or another plaid version from Madewell here)/Madewell tee (here or here)/3x1 jeans (similar from 3x1 here, JCrew here, or Gap here)/Marni heels (here in size 8)
Using thrifted or vintage pieces in a wardrobe can end up making outfits look dated or costume-y. There's nothing wrong with either but this post is about working them into a modern look.
One of the ways I've found is to make sure that at least two of the things I'm wearing are very current. I usually focus on shoes, jeans, or accessories. You can get away with any crazy shirt if you're wearing a current shape in jeans and your shoes are on point. I try to keep the new additions to my closet as unadorned as possible so that they aren't competing with my vintage or thrifted pieces. It also helps if they are expensive-looking (no need to actually shell out $$$, just forgo anything that looks cheap). This works no matter your style. Just pick your basics and choose thoughtfully.
For the above outfit I'm wearing a thrifted dress that's not quite vintage and some Marni heels from 2008 (I think. Definitely not a recent season). So I paired it with a Madewell tee and 3x1 straight leg selvedge jeans. Both are staples for me and both are in modern cuts and fabrics. Not trendy pieces but very "now", you know? They make a nice backdrop for the dress and shoes while bringing both to 2015.
So that's it. No matter what crazy thing you have hanging in your closet that you're a bit worried about wearing just pair it with at least two modern things and you'll look unique and ahead of the curve. Ta-da!