How dyou figure out what chords sound good over a riff? For example

|---------------------------------------------------------------------------|
|---------------------------------------------------------------------------|
|---------------------------------------------------------------------------|
|-----------5h7p5--4h5p4-------------5h7p5--4h5p4------------------------|
|---7b-7b-----------------5--7b--7b-----------------5/7--------------------|
|---------------------------------------------------------------------------|

I can't get chords that sound good over that riff. PPlease help. thx.