With upbeat a primary focus, let's look at some bowing patterns that will make it pop out easily. I like to accent the upbeat by beginning a slur on the upbeat and slurring into the next downbeat. Where the downbeat is placed relative to strict timing can be a variable according to geographical region and style. Southern Old-Timey music generally moves the downbeat forward, slightly in front of the beat, while in Cajun music, the downbeat is usually found slightly after the one beat. Once fairly strict about playing right on the beat, some New England players including myself have begun gravitating away from beginning the downbeat strictly on the one beat, moving it to slightly before the beat.
Some fiddlers play a slightly dotted rhythm to add more swing.
Thinking like a drummer, we ideally punch up a variety of danceable rhythms over a repeated melody line so that peopleare constantly being energized as they dance through the figures. It practically lifts the dancers through the figures when it's done effectively. It's a lot like chamber music, with listening uppermost in creating something danceable, beautiful, and fun to play. Playing for dancing is a skill that requires lead, rhythm, harmony, improvisation and listening skills as well as an intuitive reading of the dancers. Rhythm is a physical phenomenon, so it helps to be at least a part-time dancer yourself.