For me, I find that being balanced is the most important thing for return of serve. Initial momentum going forward, but when Ive seen where the ball is going and moved accordingly I create a stable base of support - feet quite wide and open stance. I concentrate on using the pace of the serve instead of generating power, and directing it. If I'm unstable and trying to wack it then things fall apart.
Probably not technically right, but it works for me, and return of serve is probably one of my stronger parts of my very recreational game.