Watch a ton of the edits that's in the "Top Rated" section, and try to pick up how the pace is holding up with the song, where they use slowmo/fastmo, fillers and so on...
The important ting is knowing what you want to make, and having a song in mind before you start the editing to kind of visualize wich direction you want it to go.
Just watch a lot of edits and try to pay attention to all the tecnical stuff. If your a beginner, you can allways watch some action editing tutorials, or websites that post triks and tips.
PS if u dont have a clue where to look for sites like that, and dont find anyting usefull at google, just PM me and ill link u up with some really usefull sites :)