There are several ways that I have noticed you can keep flow:
Motion - This doesn't neccesarily mean that there needs to be movement in every single clip, but for the most part, look for motion. And this doesn't mean that if it's moving it's right, please understand that. Look for keeping motion consistent. I find myself many times just simply flipping a clip horizontally so that the character will be moving to the right instead of left, because there was a movement to the right in the clip before it.
Pace - This one is probably one of the easiest to get down, and people will do it without even really thinking about it, but pace is extremely important. Unless you are trying to go for a certain jarring feeling or something, you're going to want to keep the pace with the music. If it's fast, show fast. If it's slow, show slow. In my opinion a song with a great buildup and then breakdown or impact is fucking awesome, and if you can show the video putting out the same feeling, of build up, and all this tension and stuff, followed by this badass breakdown.. ohhhhh yahhhh
Lyrics - Honestly IMO; Either ignore them or embrace them consistently. This isn't as huge of a factor, but it definately can help keep your flow. As a viewer I hate when a video will be like heavy lyric sync, and then will kinda just start ignoring the lyrics. If you're going to match lyrics, try and match them a consistent amount throughout the whole vid. Consistency is good.
That's all I can think of for now, I'll add on to this list if I think of more, but these are the basics I think.